Reducing False-Positives and False-Negatives in Security Event Data Using Context Derek G. Shaw August 2011

Overview of Security Monitoring Reducing False-Positives and False-Negatives in Security Event Data Using Context —2— August 2011

Purpose of Security Monitoring Reducing False-Positives and False-Negatives in Security Event Data Using Context —3— August 2011 The purpose of security monitoring is to provide real-time, up-to-the-minute security awareness of current threats, risks, and compromises as accurately as possible.

Components of Security Monitoring Reducing False-Positives and False-Negatives in Security Event Data Using Context —4— August 2011 Consoles (Analyst Desktop) Database Manager (Rules, Data Aggregation, Data Correlation, Reporting) Sensors Intrusion Detection System Log Servers Network Flows Vulnerability Scanners

The False Problem With Security Monitoring Reducing False-Positives and False-Negatives in Security Event Data Using Context —5— August 2011 False-positives Normal or expected behavior that is identified as anomalous or malicious False-negatives Conditions that should be identified as anomalous or malicious but are not

Why So Many False Positives and Who Knows Hows Many False-Negatives Reducing False-Positives and False-Negatives in Security Event Data Using Context —6— August 2011 While some false-positives and false-negatives will occur, a good portion can be attributed to lack of knowledge about the environment being monitored Not keeping knowledge about the environment up-to- date as well as historically accurate

So, how do you reduce the rate of both false-positives and false-negatives? Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —7— August 2011

What is Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —8— August 2011 Context is additional data and information that is added to security event data to increase the relevance and meaning of the data in relation to one’s environment.

Traditional Security Event Data Reducing False-Positives and False-Negatives in Security Event Data Using Context —9— August 2011

Traditional Network Flow Event Data Reducing False-Positives and False-Negatives in Security Event Data Using Context —10— August 2011 Start TimeEnd TimeSource AddressSource PortDirection :30: :30: > Destination AddressDestination PortIP ProtocolDurationFlags TCP30E Source PacketsDestination PacketsSource BytesDestination Bytes Note : /16 - Corporate Network

Traditional IDS Event Data Reducing False-Positives and False-Negatives in Security Event Data Using Context —11— August 2011 Detection TimeAlertSource AddressSource Port :30:04MS SQL Injection Attempt Destination AddressDestination PortIP Protocol TCP Note : /16 - Corporate Network

Traditional Syslog Event Data Reducing False-Positives and False-Negatives in Security Event Data Using Context —12— August 2011 DateTimeHostProcessPID Jan 113:54: SUDO34456 Message jdoe : TTY=ttys000 ; PWD=/Users/jdoe ; USER=root ; COMMAND=/bin/bash Note : /16 - Corporate Network

Traditional Security Event Data with Context Added Reducing False-Positives and False-Negatives in Security Event Data Using Context —13— August 2011

Network Flow Event Data with Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —14— August 2011 Start TimeEnd TimeSource AddressSource PortSource Network :30: :30: Unused DirectionDestination AddressDestination PortDestination NetworkIP Protocol -> ChinaTCP DurationFlagsSource PacketsDestination PacketsSource Bytes 30E Destination BytesAlertAsset Tags 12453Destination Address on Malware Watch ListUnknown Note : /16 - Corporate Network

IDS Event Data with Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —15— August 2011 Detection TimeAlertSource AddressSource Port :30:04MS SQL Injection Attempt Source NetworkDestination AddressDestination PortDestination NetworkIP Protocol Brazil Printer Network TCP Asset Tags Printer, No-Internet Note : /16 - Corporate Network

Syslog Event Data with Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —16— August 2011 DateTimeHostHost NetworkProcess Jan 113:54: Financial SUDO PIDMessage 34456jdoe : TTY=ttys000 ; PWD=/Users/jdoe ; USER=root ; COMMAND=/bin/bash AssetAlertUser Info Linux, Financial, DB, RestrictedUser not authorized for SUDO on host John Doe, Mail Room Staff Note : /16 - Corporate Network

Types of Networks Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —17— August 2011 Access tags (Internal, Private, External, No-Internet) Dark space tags for unused IP space Subnet descriptions

Types of Asset Context Reducing False-Positives in Security Event Data Using Context —18— August 2011 Business Role Tags (Financial, HR, Printers) Operating System Software Category Tags (Apache, BIND, MySQL) System Classification Tags (SSH Server, LDAP Server, Web Server, DNS)

Types of User Context Reducing False-Positives in Security Event Data Using Context —19— August 2011 Real Name Working group (Mail Room, Control Room, Networking Group) List of accounts List of privileged access accounts

How Context is Implemented Reducing False-Positives and False-Negatives in Security Event Data Using Context —20— August 2011

Context Data Sources Reducing False-Positives and False-Negatives in Security Event Data Using Context —20— August 2011 Memory-resident key/value data stores Contains data about assets, networks, and users Continually updated by data mining scripts

Context Preprocessor Reducing False-Positives and False-Negatives in Security Event Data Using Context —22— August 2011 Sits between the sensors and security monitoring system manager Queries the context data sources in real-time based on IP addresses or user names Appends any context data available to event data record

Important Things to Remember Reducing False-Positives and False-Negatives in Security Event Data Using Context —23— August 2011 For context to be effective, it must be current. For events to be accurately reflected in your environment, context cannot be treated as on-demand in the manager. Context for a given event must be recorded once and not changed. Treating context as on-demand in the manager may turn an alert into a false- negative.

Advantages of Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —24— August 2011 Adds additional data and information to the event record that the sensor does not have. Updates to context data sources can be automated and dynamic.

Advantages of Context (cont.) Reducing False-Positives and False-Negatives in Security Event Data Using Context —25— August 2011 Changes to your environment can be reflected in updating the context data; requiring less changes to security monitoring rules and filters Security monitoring rules and filters can be created for context. This eliminates or reduces the need to create filters and rules based on lists of IP addresses, one-off rules, and filter exceptions.

Disadvantages of Context Reducing False-Positives and False-Negatives in Security Event Data Using Context —26— August 2011 Requires analysts to understand the IT infrastructure Requires constant upkeep to stay relevant Extra process in security monitoring workflow

Questions? Comments? Reducing False-Positives and False-Negatives in Security Event Data Using Context —27— August 2011