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

2. Guide to Network Defense and Countermeasures, Second Edition2 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 Edition3 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 Edition4 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 Edition5 Rule Actions (continued) Snort actions for rules –Alert –Log –Pass –Activate –Dynamic

6. Guide to Network Defense and Countermeasures, Second Edition6 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 Edition7 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 Edition8 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 Edition9 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 Edition10 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 Edition12 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 Edition13 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 Edition14 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 Edition15 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 Edition16 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 Edition17 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 Edition18 How to Respond: The Incident Respond Process Steps –Preparation –Notification –Response –Countermeasures –Recovery –Follow-Up

19. Guide to Network Defense and Countermeasures, Second Edition19 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 Edition20 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 Edition22 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 Edition23 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 Edition25 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 Edition27 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 Edition28 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 Edition29 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 Edition30 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 Edition31 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 Edition32 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 Edition33 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 Edition34 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 Edition35 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 Edition37 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 Edition38 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 Edition39 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 Edition40 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 Edition41 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 Edition42 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 Edition44 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 Edition45 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 Edition46 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 Edition47 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 Edition48 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