network vulnerability assessments lessons learned chris goggans [email protected]
TRANSCRIPT
What are Vulnerability Assessments?
Internal and external attacks Validation of existing security mechanisms Detailed analysis of all networked devices and
services Audits for policy compliance and deficiencies in
existing policies Prioritized recommendations for improving
security posture
Vulnerability Assessments: WHY?
Only realistic way to determine vulnerabilities Get a baseline of vulnerability state Prioritize remedial actions Correct serious problems quickly Assure that policies address real vulnerabilities Industry best practice
Vulnerability Assessments: HOW?
External Assessment – Internet– Modems– Wireless– Partner Connectivity
In-briefing Internal Assessment Out-briefing Report preparation and delivery Executive briefing
Government Contractor Unpassworded TELNET access into print server SNMP Read/Write community string exposed in printer
configuration menu Community string also used on devices such as routers, switches, etc. “Level 7” hashes in Cisco config files exposed the password
“mbhafnitsoscar” This password also used by Domain Administrator on Windows PDC Windows Domain also tied to NetWare eDirectory, sharing account
names and passwords In total, compromise of nearly 15,000 accounts and 99.99% of all
systems and network devices…all from one insecure printer
Government ContractorLessons Learned:
Even the most insignificant network device can provide information that uncovers a major attack path – Always examine everything connected to your networks!
Always utilize the greatest password protection possible– MD5 vs Level7
In situations where accounts and passwords are shared across platforms, a single compromise of the weakest platform can lead to massive compromise– Rainbow Tables & NTLMv1
Civilian Government Agency
Development WWW server running with default cold fusion scripts that allow remote viewing of web source
Attack Path 1– ODBC setup in web page source code exposed z/OS RACF account and password
used for DB2 queries– Account found to have “system programmer” access on IBM Mainframe
Attack Path 2– MS-SQL “sa” account and password in web source– SQL “XP_CMDSHELL” stored procedure gave remote “SYSTEM” access to
Windows OS– Local SAM file exposed Domain Administrator account– SAM file on PDC had roughly 50,000 accounts– Certain users used same password on Windows as they did on very large High
Performance Computing cluster
Civilian Government AgencyLessons Learned: Passwords embedded in web applications are never a
good thing Web Application Vulnerability Assessments have
become as important as Network Vulnerability Assessments
Database security is also critical and often left unchecked
Another Government Agency
Large network of Solaris and Windows systems All machines and applications patched Many important UNIX services are TCP-wrapped
– NFS, NIS, etc. Customer had recently deployed new KVM switches in their racks In addition to 3rd party software, KVM Switch also had HTTPS based
management interface with a default “Admin” account with no password HTTPS-based access also provided JAVA-based remote console program Open consoles found on Windows system (as Administrator) and Solaris system
(as root) NIS passwd-byname tables and Windows SAM and locally cached account
hashes pulled All systems compromised
Another Government AgencyLessons Learned: Every host on a network must undergo some level of
security hardening before being allowed to connect to the production network
Every console should be forced to either screen-lock or auto-logout when not in use
Managed Service Provider
Customer had limited Internet exposure, primarily HTTP traffic allowed to “Hosting” LAN (primarily only TCP 80 & 443)
Web server compromised with Apache “Chunked-code vulnerability”
Server had 3 interfaces (2 for normal access, 3rd interface leading to NOC management-LAN for “out of band” SNMP)
System on NOC network compromised with common Windows vulnerability
NOC network had visibility into entire corporate network, as well as other hosted customers
Managed Service ProviderLessons Learned:
It only takes one vulnerable service to give attackers a strong foothold into your network
Management networks or VLANs are often excellent points to bridge between networks without direct connectivity
Systems hosted by 3rd parties are often compromised by attacks originating from less secure customers at the same hosting facility
Telecommunications
Large US telephone company Dial-ups found with unpassworded
pcAnywhere pcAnywhere system used primarily for
access into security camera monitoring of unmanned facilities
Full access to internal network, including switching systems, billing, etc.
TelecommunicationsLessons Learned:
Modems can still be a major external threat!
Critical systems should be firewalled against general network access
Emergency Response
Organization responsible for state-wide emergency medical services
Internet connectivity shared with major university Organization tied to other state-run networks through
dedicated lines Firewall rules allowed certain hosts on University
network & State Government networks into EMS network using insecure protocols (MS-SQL, SMB)
Common exploits led to massive compromise
Emergency ResponseLessons Learned: All inbound partner connections should be
examined as part of a vulnerability assessment Firewall rules should likewise be examined to
uncover any potential weak points for permitted communications
Your network is ultimately only as secure as the weakest host connected to you
Law Enforcement
Compromised Windows Workstation through un-patched IIS Web server – obtained local SAM file with domain accounts
Compromised Windows PDC by escalating privileges with access gained from previous machine
Compromised Investigator’s workstation with Domain Admin rights
Workstation had VNC remote control software – password retrieved from Windows registry
Logged in using remote control GUI Icon on desktop for MILES/NCIC
– Just a keystroke capture program away from access to the FBI
Law EnforcementLessons Learned: Users should not be allowed to install random
applications on their workstations– Especially those that facilitate remote control!
Applications that utilize proprietary authentication are usually easily broken
Any system with multiple Network Connections can be used as a gateway to bridge secure networks to insecure networks– The same holds true for VPNs, PPP connections, Wireless LAN
access, etc.
Even one of the most “secure” systems in the US can be compromised if accessed in an insecure fashion
Uncovering Attacks During Assessment
Many assessments will reveal existing evidence of prior attack activity
Some attacks may be more serious than others
Most attack information found on Internet-based hosts are from random hacker groups running scripts
Attacks found on internal machines are usually much more serious
Real Incident – Local Government
Internet assessment found that IIS server was vulnerable to attack
Several strange files found in the “SCRIPTS” directory
Files were backdoor CMD shells and host scanning scripts
Web log analysis showed that the host had been compromised by at least two separate groups: one in USA, one in Korea
Host was patched and files were removed
Real Incident – Service Provider
Customer had servers hosted at Tier-1 internet provider Poor password on MSSQL server led to compromise of
machine Customer noticed that the server was losing disk space Hidden directories had over 30GB of movies and music Netstat output showed that server was connecting to IRC
server Ethernet Sniffing revealed IRC channel and channel key
being used IRC Channel was being used by German software pirates We joined the channel and surprised the pirate group. They
apologized and told us we could keep copies of the movies.
Real Incident - Telephone Company
Systems Administrator making threats
about taking down Telephone switches
Multiple root-shell files found on critical
UNIX servers throughout the enterprise
Backdoor access to switching systems
found through X.29 PADs
Administrator’s contract was terminated
Real Incident – Web Services
Systems administrator fired for sexual harassment Windows machines began experiencing problems False accounts discovered on Internet accessible
machine Trojan Horse discovered on internal workstations Real motive was intellectual property theft, and
administrator was arrested
Real Incident - Banking
Vulnerability assessment conducted against bank network
Trojan Horse discovered on workstation Workstation used primarily as database for
all customer credit-card data No data available to identify how Trojan
Horse was delivered All credit cards on server had to be re-
issued
Common Assessment Problems
Customer Perception Misconfigured Hosts Bad Programming
Problem – Customer Perception Customer knew that we had gained access to all
UNIX systems Administrator complained that TACACS server
no longer worked, and thought our assessment caused the issue
Review of TACACS config file showed that it had been recently modified by the Administrator
We discovered that the Administrator had put in an additional # in file that caused the problem
Administrator was very embarrassed
Problem – Misconfigured Hosts Solaris file system became full and caused kernel panic Problem occurred when the server was port scanned, starting
somewhere above 30000 /var/log/messages file showed that “Inetd” process was failing
and writing hundreds of errors per minute to file, causing the disk usage
Analysis of /etc/inetd.conf file showed that a process (kcms_server) was allowed to spawn by inetd on port 32774
Examination of files showed that the kcms_server program (and many other unused programs) had been erased by system integrator during original install
Addition of a single # in inetd before the program name corrected the problem
Problem – Bad Programming Port scans of a host indicated multiple unknown
applications running on database server When connecting to these services with netcat or
telnet to obtain banner and protocol information, the service crashed
Analysis of the source code indicated that application programmers did not put in any error handling routines for TCP connections
Programmers were able to fix the issue very quickly
Final Thoughts Insecure Web Applications have become one of the biggest
targets for attackers. Modems (authorized and unauthorized) are still not receiving the
attention they deserve as potential threats. Patch & Configuration management are consistently neglected,
or only applied to Core OS (not applications). The concepts of Internal and External access have begun to blur:
– Partner connections– Inbound “Phishing” emails and Web Pages downloading malicious code
that open up outbound “shell” access
Poor passwords are the number one mechanism to gain host-level access.