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Intrusion Detection Methods

Intrusion Detection Methods. “Intrusion detection is the process of identifying and responding to malicious activity targeted at computing and networking resources.”. The Seven Fundamentals. What are the methods used How are IDS organized What is an intrusion

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Intrusion Detection Methods

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  1. Intrusion Detection Methods “Intrusion detection is the process of identifying and responding to malicious activity targeted at computing and networking resources.”

  2. The Seven Fundamentals • What are the methods used • How are IDS organized • What is an intrusion • How do we trace and how do they hide • How do we correlate information • How can we trap intruders • Incident response

  3. Some fundamental questions • Are ID methods only suited for manual use by experts? • Are ID methods well defined enough to be automated? • What are some of the manual methods used by experts? • What ID methods are available in tools today?

  4. ID methods • Audit trail processing • On-the-fly processing • Profiles of normal behavior • Signatures of abnormal behavior • Parameter pattern matching or anomaly discovery Are the above methods independent? Dependant? Mutually exclusive?

  5. Audit Trail Processing • Activities are first logged and stored in a log file via audit probs. • Audit probes are [mostly] selected based on what constitutes security critical events. • System and security administrators (and designers) are changed with enabling/disabling probs. Auditing vs. Performance? What are the issues? What are the TCSEC requirements for Audit? (See Page 40)

  6. Case study: TCP logs <src_ip, dst_ip, src_port, dst_port, protocol, time, direction, status> Router/ Gateway Internal net (in) External net (out) log

  7. Case study: TCP logs (cont.) <in,in, 4050, 80, tcp, 07:02:22, inbound, success> <outx,gw, 6025, 23, tcp, 07:51:12, inbound, failure> <outx,gw, 6025, 23, tcp, 07:51:55, inbound, failure> <outx,gw, 6025, 23, tcp, 07:52:17, inbound, failure> <outx,gw, 6025, 23, tcp, 07:52:58, inbound, failure> . . . <outx,in, 3000, 23, tcp, 13:04:22, inbound, success> <outy,gw, 6025, 23, tcp, 23:54:22, inbound, success>

  8. How much of the previous discussion can be automated?

  9. Examples of things to watch for! • Users logging in at strange hours • Unexpected reboots or clock changes • Unusual error messages • Failed login attempts • Unauthorized use of the su command • Users logging from unusual locations

  10. Problems to be considered while using logging systems Most administrators don’t collect audits, and if they do, they rarely process them!

  11. Problems to be considered while using logging systems (cont.) • Large size of audit files • About 5M per week for a workgroup server • Becomes more problematic for centralized logging

  12. Problems to be considered while using logging systems (cont.) • Degraded system performance • Reached 85% on some typical unix and NT systems http://www.iamsam.com/papers/thesis/thesis.htm

  13. Problems to be considered while using logging systems (cont.) • Difficulty in protecting the log • Log files growing smaller! • Print everything

  14. Problems to be considered while using logging systems (cont.) • Unknown storage duration of logs • How long should logs be kept? • How long are they kept on your linux system?

  15. Unix Syslog • Syslogd is a daemon (background process) • Receives message for the log file from: • User processes running on the same mchaine (as syslogd) via /dev/log • Kernel routines (/dev/klog) • Processes on another machine via UDP port 514 • Syslogd defines an associated API for application authors

  16. /etc/syslog.conf # Log all kernel messages to the console. # Logging much else clutters up the screen. kern.* /dev/console # Log anything (except mail) of level info or higher. # Don't log private authentication messages! *.info;mail.none;news.none;authpriv.none /var/log/messages # The authpriv file has restricted access. authpriv.* /var/log/secure # Log all the mail messages in one place. mail.* /var/log/maillog # Everybody gets emergency messages, plus log them on another # machine. *.emerg * # Save mail and news errors of level err and higher in a # special file. uucp,news.crit /var/log/spooler

  17. /var/log/messages F25 21:37:44 rnd PAM_pwdb[17775]: (sshd) session opened for user sherif by (uid=0) F25 21:40:00 rnd CROND[17784]: (root) CMD ( /sbin/rmmod -as) F25 21:42:18 rnd PAM_pwdb[17789]: (sshd) session opened for user sherif by (uid=0) F25 21:50:01 rnd CROND[17813]: (root) CMD ( /sbin/rmmod -as) F25 21:51:24 rnd PAM_pwdb[17789]: (sshd) session closed for user sherif F25 21:52:27 rnd PAM_pwdb[17775]: (sshd) session closed for user sherif F25 22:00:00 rnd CROND[17851]: (root) CMD ( /sbin/rmmod -as) F25 22:01:00 rnd CROND[17856]: (root) CMD (run-parts /etc/cron.hourly) F25 22:10:00 rnd CROND[17887]: (root) CMD ( /sbin/rmmod -as) F25 22:20:01 rnd CROND[17969]: (root) CMD ( /sbin/rmmod -as) F25 22:30:00 rnd CROND[17999]: (root) CMD ( /sbin/rmmod -as) F25 22:40:01 rnd CROND[18034]: (root) CMD ( /sbin/rmmod -as) F25 22:50:00 rnd CROND[18061]: (root) CMD ( /sbin/rmmod -as) F25 23:00:00 rnd CROND[18087]: (root) CMD ( /sbin/rmmod -as) F25 23:01:01 rnd CROND[18092]: (root) CMD (run-parts /etc/cron.hourly) F25 23:10:01 rnd CROND[18123]: (root) CMD ( /sbin/rmmod -as) F25 23:20:00 rnd CROND[18149]: (root) CMD ( /sbin/rmmod -as) F25 23:30:00 rnd CROND[18175]: (root) CMD ( /sbin/rmmod -as) F25 23:40:00 rnd CROND[18201]: (root) CMD ( /sbin/rmmod -as) F25 23:50:01 rnd CROND[18228]: (root) CMD ( /sbin/rmmod -as) F26 00:00:00 rnd CROND[18264]: (root) CMD ( /sbin/rmmod -as) F26 00:01:01 rnd CROND[18269]: (root) CMD (run-parts /etc/cron.hourly) F26 00:10:00 rnd CROND[18302]: (root) CMD ( /sbin/rmmod -as) F26 00:20:01 rnd CROND[18352]: (root) CMD ( /sbin/rmmod -as) F26 00:28:17 rnd PAM_unix[18386]: (system-auth) session opened for user root by sherif(uid=500) F 26 00:30:00 rnd CROND[18426]: (root) CMD ( /sbin/rmmod -as)

  18. /var/log/mail F25 22:32:22 rnd sendmail[18009]: g1PKU1x18007: to=<sallysherif@yahoo.com>, delay=00:02:21, xdelay=00:00:03, mailer=esmtp, pri=589605, relay=mx2.mail.yahoo.com. [64.157.4.88], dsn=2.0.0, stat=Sent (ok dirdel) F25 22:32:42 rnd sendmail[18009]: g1PKU1x18007: to=<mhamama@realtyagent.com>, delay=00:02:41, xdelay=00:00:20, mailer=esmtp, pri=589605, relay=ob-mail-com.mr.outblaze.com. [205.158.62.26], dsn=2.0.0, stat=Sent (g1PJVqt94451 Message accepted for delivery)

  19. SWATCH • Simple and effective tool • Written in perl /pattern/[, /pattern/] action[,action]duration

  20. Case Study : Secureview Firewall-1 Audit Intranet Internet Firewall-1 Firewall-1 log Database Builder Data Mart Reporting Module Other Firewall-1 Log Processing Tools Admin Module SecureIT SecureView Security Administrator

  21. Mar 2 23:53:51 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 2 23:54:33 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 2 23:55:39 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 2 23:56:44 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 2 23:57:50 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 2 23:58:49 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 3 00:00:00 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 3 00:01:01 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 3 00:02:05 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 3 00:03:11 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P*** Mar 3 00:04:14 148.63.149.144:1072 -> 208.160.134.38:1214 VECNA ****P***

  22. Intrusion Detection System Target System Direct system feeds on-the-fly processing Probe Ponts selected by system administrators On-the-fly processing • Timeliness • Processing method • Storage requirements • Information capacity

  23. Network management and NIDS • Use SNMP and RMON (RFC 1271) as a basis for ID collection and processing • Analyze traffic history and statistics • Examine network trends • initiate alarms • Traffic generation for testing

  24. Enterprise WAN(SNMP transport) LanProbe LAN(Ethernet) Netmetrix Analysis applications for trending, alarms, analysis, display, etc LAN(token ring) LanProbe Noninvasive monitors

  25. Case Study : NFR GUI Decision Engine Backend Target System Packet Sucker Query Filter 1 Backend Filter 2 Filter 3 Backend Filter N Alert Manager

  26. Methods for extracting traffic from the network for processing • In-line diversion of traffic by network components • Off-line extraction (passive sniffing) • Most used: Ethernet promiscuous mode • Other examples: • Serial lines • Wireless networks • Tempest effect aka The van Eck effect

  27. Case Study : BorderGuard Firewall Extraction for NetRanger Processing • NSX device : local intrusion Monitoring Function Gateway Traffic Protected System Target System BorderGuard Firewall Diverted Traffic for NetRanger Intrusion Detection NSX Intrusion Detection

  28. Security Administrator Refine User Profile Update User Activity Knowledge Base (Comparable users) User Profiling Method Normal Behavior profiling

  29. Normal Behavior profiling • Initial profiling of new systems and users based on estimations of expected behavior • Observed user and system behavior should be used to fine-tune profiles • Information from other (external) resources is used to improve the accuracy of prediction

  30. System Activity Activity Expected (Profiles) Activity Observed (audit log) Compare and Respond Concept of Profile-based Processing

  31. System Activity Audit Trail User/System Profiles Alarms Anomaly Records IDES Processing IDES Design Case study: IDES model • Audit trail information is collected in protected logs • Profile based tools as used for off-line analysis

  32. Case study: IDES model (cont.) <subject, object, profiles, audit-records, anomaly records, alarms> • Subjects and Objects: from classical INFOSEC view of the initiator and the target of an activity

  33. Case study: IDES model (cont.) • Profile: Characterization of behavior • Audit records: the data structures used to capture the system’s observed behavior • Anomaly records: the data structures used to capture anomalous behavior • Alarms: problem reporting methods

  34. Toll fraud and similar problems • How can toll fraud-like problems be solved using “Normal Behavior profiling?” • How about credit card fraud? • Phone card fraud?

  35. http://www.atcomm.com/advisor/basics/call-account.htm • Boost Security • Highlight Suspicious Activity and Review Unrecognizable Call Data for Hacker Detection • Prevent/Locate Unauthorized System Access • Real Time Notification of Exception Calling • Track After Hours Security Guards • Detect Bomb Threats • Selective Reporting/Display for Top Secret/Sensitive Materials • Account for Calls But Delete Detail (Call Processing) • Password Security to Prevent Moving from Call Processing • Keyboard Macro Available to Provide Additional Security

  36. The Abnormal Behavior (Attack) Signature Method • Commonly used in on-the-fly IDS • Attack signatures • May require temporal and state machine like modeling • Special character strings • E.g.: /etc/password in an ftp session

  37. Target System Strings Intrusion Detection Systems Profiles Probe Point Feed Should correlate string and profile based processing Selected via traffic content modeling of attack Selected via activity sequence modeling of attack

  38. Case Study: SNORT rules • http://www.snort.org/docs/writing_rules/

  39. alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"FTP .forward"; content: ".forward"; flags: A+;reference:arachnids,319; classtype:suspicious-filename-detect; sid:334; rev:2;) alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"FTP .rhosts";flags: A+; content:".rhosts"; reference:arachnids,328; classtype:suspicious-filename-detect; sid:335; rev:2;) alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"FTP CWD ~root"; content: "cwd ~root"; nocase; flags: A+;reference:arachnids,318; classtype:bad-unknown; sid:336; rev:1;) alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"FTP EXPLOIT aix overflow";flags: A+;dsize:>1300; content:"CEL "; reference:arachnids,257; classtype:attempted-admin; sid:337; rev:1;) alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"FTP EXPLOIT format string"; flags: A+; content: "SITE EXEC |25 30 32 30 64 7C 25 2E 66 25 2E 66 7C 0A|"; depth: 32; nocase; reference:arachnids,453; classtype:attempted-user; sid:338; rev:1;)

  40. Parameter pattern matching or anomaly discovery • Based on continuous monitoring of network and systems attributes • The monitoring is not necessary security focused • The use of day-to-day operational experience and the basis for detecting anomalies

  41. Intrusion Detection System Target System (network, OS,application, etc Interpretations of Patterns (intrusion detection) Operational View (Patterns) Noarmal Operations Normal system Operation and Administration This interpretation is triggered by and detection of change from normal These monitoring operations may not be disciplined or predictable

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