Network Vulnerability Assessments: Lessons Learned

Network Vulnerability Assessments Lessons Learned Chris Goggans [email_address]

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: H OW ? 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 Contractor Lessons 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 Agency Lessons 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 3 rd 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 Agency Lessons 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, 3 rd 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 Provider Lessons 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 3 rd 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.

Telecommunications Lessons 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 Response Lessons 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 Enforcement Lessons 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.

Network Vulnerability Assessments: Lessons Learned

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Network Vulnerability Assessments: Lessons Learned