Guide to Network Defense and Countermeasures Second Edition

1. Guide to Network Defense and Countermeasures Second Edition Chapter 8 Intrusion Detection: Incident Response

2. Guide to Network Defense and Countermeasures, Second Edition 2 Objectives Configure an IDS and develop filter rules Develop a security incident response team for your organization Explain the six-step incident response process Describe how to respond to false alarms to reduce reoccurrences Explain options for dealing with legitimate security alerts

3. Guide to Network Defense and Countermeasures, Second Edition 3 Developing IDS Filter Rules IDS effectiveness depends on its database Database should be complete and up to date IDS can have its own set of rules You can edit it in response to scans and attacks IDS can be used proactively Block attacks Move from intrusion detection to intrusion prevention

4. Guide to Network Defense and Countermeasures, Second Edition 4 Rule Actions IDS has a passive and reactive nature Configure IDS to take actions Other than simply triggering alarms Provides another layer of network defense IDSs include documentation for writing rules Customized rules can increase false positives during the learning process Test your rules before using them in a real system

5. Guide to Network Defense and Countermeasures, Second Edition 5 Rule Actions (continued) Snort actions for rules Alert Log Pass Activate Dynamic

6. Guide to Network Defense and Countermeasures, Second Edition 6 Rule Data Specify the action you want Snort to perform Specify the rest of the data that applies to the rule Protocol Source and destination IP addresses Port number Direction

7. Guide to Network Defense and Countermeasures, Second Edition 7 Rule Options Make Snort more precise Options are enclosed in parentheses Snort options msg ttl id flags ack content logo

8. Guide to Network Defense and Countermeasures, Second Edition 8 Rule Options (continued) TCP flags are designated by a single character Rule base for an IDS is different from a packet-filtering rule base IDS rules assume packets have been already filtered Log any traffic that gets through the packet filter And matches a signature in the IDS

9. Guide to Network Defense and Countermeasures, Second Edition 9 Developing a Security Incident Response Team (SIRT) Response options Taking countermeasures to block intrusion Making corrections to packet-filtering rules and proxy servers Modifying security policies to cover new vulnerabilities Security Incident Response Team (SIRT) Gives your organization flexibility to carry out these response options

10. Guide to Network Defense and Countermeasures, Second Edition 10 Goals of a Security Incident Response Team (SIRT) Security Incident Response Team (SIRT) Known as computer incident response team (CIRT) Group of people assigned to respond effectively to security breaches Primary functions Preparation Notification Response Countermeasures Recovery Follow-up

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12. Guide to Network Defense and Countermeasures, Second Edition 12 Responsibilities of Team Members Look within the organization for SIRT members SIRT members should stop any work they have To respond to a security incident They should have enough authority to take decisions Deciding what roles team members will assume SIRT should contain employees representing a cross-section of the organization This ensures all parts of the organization are represented

13. Guide to Network Defense and Countermeasures, Second Edition 13 Responsibilities of Team Members (continued) Typically, SIRT members come from Management Legal Information Technology (IT) Physical security Information Security Services (ISS) Human Resources (HR) Public Relations (PR) Finance/Accounting

14. Guide to Network Defense and Countermeasures, Second Edition 14 Responsibilities of Team Members (continued) Staffing and training Virtual team Consists of employees with other jobs Team exists only during meetings or when an incident becomes serious enough Tends to get out of touch and need retraining If budget allows it, assemble a team whose sole responsibility is security incident response Might be economically feasible only to large organizations

15. Guide to Network Defense and Countermeasures, Second Edition 15 Responsibilities of Team Members (continued) Staging Fire Drills Conduct a security drill You might need to convince upper management Drills can pay off in the long run Making response more effective and coordinated Pick a time for the drill and follow a scenario Drills can be scheduled or spontaneous Intended to identify any holes in security procedures And make sure SIRT members know their duties and responsibilities

16. Guide to Network Defense and Countermeasures, Second Edition 16 Public Resource Teams Teams around the world publish notices and articles about serious security incidents You can notify these teams if you encounter a significant security event These groups also provide training for response team members CERT Coordination Center DFN-CERT

17. Guide to Network Defense and Countermeasures, Second Edition 17 Outsourcing Incident Response Hire a company that monitors your network and IDS sensors Tells you whether an intrusion has occurred Advantages Result in lower overall costs Disadvantages Hard to achieve timely, effective incident response Get references from current and former customers before hiring an incident response service

18. Guide to Network Defense and Countermeasures, Second Edition 18 How to Respond: The Incident Respond Process Steps Preparation Notification Response Countermeasures Recovery Follow-Up

19. Guide to Network Defense and Countermeasures, Second Edition 19 Step 1: Preparation Using risk analysis to prepare your responses Risk analysis identifies what needs to be protected It is used to prepare a security policy Use security policy as a guideline when responding to incidents Many security policies include a section on incident response Everyone involved in incident response should know where these guidelines are

20. Guide to Network Defense and Countermeasures, Second Edition 20 Step 1: Preparation (continued) Active network monitoring Essential activity SIRT members might be dedicated to this task Considered a proactive task Can prevent incidents from occurring Can reduce false positives Involves actively testing your network Use a network vulnerability analyzer Security Administrator’s Integrated Network Tool (SAINT) WebSAINT Nessus

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22. Guide to Network Defense and Countermeasures, Second Edition 22 Step 2: Notification Process by which SIRT members receive news about security incidents Notifications come from Firewalls or IDSs SIRT members Network administrators Employees After notification, SIRT members should assess level of damage Not all incidents should be reported to all SIRT members

23. Guide to Network Defense and Countermeasures, Second Edition 23 Step 3: Response SIRT members should keep in mind Do not panic Follow established procedures Take time to analyze all reported events Do not simply react Important to have clear escalation procedures Key to efficient response Create a flowchart for the escalation procedures

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25. Guide to Network Defense and Countermeasures, Second Edition 25 Step 3: Response (continued) Determining the need for escalation Determine What needs to be reported Who needs to know it How quickly you need to do the reporting Report the basic facts surrounding the incidents Figure out how people will be notified Out-of-band notification using other communication devices Consider reporting to the community serious security incidents

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27. Guide to Network Defense and Countermeasures, Second Edition 27 Step 3: Response (continued) Following standard response procedures Avoid contacting everyone by e-mail Attacker can be in control of your mail servers Set up a hotline Set up a list of people to contact Try not to overreact to intrusions Follow procedures in place that tell you exactly what to do for each situation

28. Guide to Network Defense and Countermeasures, Second Edition 28 Step 4: Countermeasures Containment of damage Containment Preventing spreading to other resources Consider doing the following Shut down the affected system Disable user and group accounts Disable services that were exploited Make backups of affected systems to protect the originals as evidence Define a set of containment procedures

29. Guide to Network Defense and Countermeasures, Second Edition 29 Step 4: Countermeasures (continued) Eradication of data introduced by an intrusion Eradication Removing any files or programs that resulted from the intrusion Can be tedious and time consuming SIRT members should do the following Check user accounts to make sure no additional users have been added Check services Check .dll files and the Windows Registry Make sure files created during the attack are legitimate

30. Guide to Network Defense and Countermeasures, Second Edition 30 Step 5: Recovery Putting compromised items back in service Monitor restored devices for at least 24 hours Make sure network is operating properly SIRT members can require users to sign a document Agreeing the computer has been serviced and returned in working order Adjust packet-filtering rules To block communications to or from Web sites involved in the attack

31. Guide to Network Defense and Countermeasures, Second Edition 31 Step 6: Follow-Up Follow-up Process of documenting What took place after an intrusion was detected And a response occurred Prevents similar intrusions from reoccurring Recordkeeping Recording all events associated with security incident Helps fellow SIRT members deal with similar situations

32. Guide to Network Defense and Countermeasures, Second Edition 32 Step 6: Follow-Up (continued) Recordkeeping (continued) Do not keep your notes on your computer Documentation is essential for prosecuting offenders Reevaluation policies You can recommend changes to the security policy based on previous attacks Information should be included in a follow-up database Details on security incidents are for internal use only Security policy should state this Prevent bad public relations

33. Guide to Network Defense and Countermeasures, Second Edition 33 Dealing with False Alarms Minimize false positives and false negatives Essential part of managing an IDS Tuning your system can degrade its performance Better to adjust existing rules if needed Create new rules only if absolutely necessary

34. Guide to Network Defense and Countermeasures, Second Edition 34 Filtering Alerts To reduce false alarms adjust rules used by Firewalls Packet filters IDSs Exclude specific signature from connecting to a selected IP address Both internal and external addresses Can even exclude an entire subnet or network

35. Guide to Network Defense and Countermeasures, Second Edition 35 Disabling Signatures You might want to disable entire signatures So they do not trigger alarms Disable signatures when testing your network False alarms should be recorded on a tracking chart Exclude duplicated signatures from IDSs To improve efficiency

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37. Guide to Network Defense and Countermeasures, Second Edition 37 Dealing with Legitimate Security Alerts Determine whether the attack is a false alarm Look for indications such as You notice system crashes New user accounts suddenly appear on the network Sporadic user accounts suddenly have heavy activity New files appear, often with strange file names A series of unsuccessful logon attempts occurs Respond calmly and follow established procedures Call law enforcement personnel if necessary To handle the intrusion

38. Guide to Network Defense and Countermeasures, Second Edition 38 Assessing the Impact Was any host on your network compromised Determine the extend of the damage Determine the scope and impact of the problem Determine if the firewall was compromised If firewall was compromised, computers on network could be accessed Reconstruct firewall from scratch

39. Guide to Network Defense and Countermeasures, Second Edition 39 Developing an Action Plan Action plan might involve the following steps: Assess seriousness of the attack Notify team leader immediately Begin to document all actions Contain the threat Determine the extend of the damage Make a complete bit-stream backup of the media If you plan to prosecute Eradicate the problem Restore the system Record a summary of the incident

40. Guide to Network Defense and Countermeasures, Second Edition 40 Handling Internal Versus External Incidents Intrusions and security breaches often originate from inside an organization Your response needs to be more measured Avoid notifying the entire staff Human Resources and Legal departments should be made aware of the problem Notify the entire staff only when they need to know something serious happened

41. Guide to Network Defense and Countermeasures, Second Edition 41 Taking Corrective Measures to Prevent Reoccurrences Take steps to prevent intrusions from recurring Set up intrusion rules that send alarms when the same intrusions are detected Notify others on the Internet about your attack

42. Guide to Network Defense and Countermeasures, Second Edition 42 Working Under Pressure Incident response activities need to be carried out with discretion Sometimes it is best to allow the incident to continue for a while This gives you time to monitor the attack Gather evidence according to the goal of your actions Prosecution Corrective measures Do not rush to respond to incidents

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44. Guide to Network Defense and Countermeasures, Second Edition 44 Gathering Data for Prosecution Rules to handle evidence Make sure two people handle the data at all times Write everything down Lock it up! Chain of custody Record of who handled an object to be used as evidence in court Decide SIRT members that will handle the evidence Before an incident occurs, decide whether you will prosecute or not Include this in your security policy

45. Guide to Network Defense and Countermeasures, Second Edition 45 Gathering Data for Prosecution (continued) Steps for handling and examining hard disks and other computer data Secure the area Prepare the system Examine the system Shut down the system Secure the system Prepare the system for acquisition Examine the system Connect target media Secure evidence

46. Guide to Network Defense and Countermeasures, Second Edition 46 Summary IDS devices can have their own set of filter rules SIRT members should come from all major departments Incident response steps Preparation Notification Response Countermeasures Recovery Follow-up

47. Guide to Network Defense and Countermeasures, Second Edition 47 Summary (continued) Response procedures should be stated in a document SIRT members should assess the level of the incident Types of countermeasures Containment Eradication After eradication is complete, affected media need to be recovered And monitored for a couple of days

48. Guide to Network Defense and Countermeasures, Second Edition 48 Summary (continued) False alarms are almost inevitable with any IDS Reduce them adjusting rules in your security devices Legitimate attacks require a calm, systematic, and thorough response External attacks by attackers you can identify might call for prosecution in court