Log Correlation Engine 3.4 Log Normalization Guide July 29, 2010 (Revision 3)

Transcription

1 Log Correlation Engine 3.4 Log Normalization Guide July 29, 2010 (Revision 3) The newest version of this document is available at the following URL:

2 Table of Contents TABLE OF CONTENTS... 2 INTRODUCTION... 3 LOG PARSING AND NORMALIZATION... 3 SEARCHING LOG DATA FROM THE COMMAND-LINE WRITING LOG CORRELATION ENGINE PLUGINS FOR MORE INFORMATION ABOUT TENABLE NETWORK SECURITY Copyright , Tenable Network Security, Inc. 2

3 Introduction This document discusses writing plugins for Tenable Network Security s Log Correlation Engine 3.4. Please share your comments and suggestions with us by ing them to support@tenable.com. It is assumed that the reader has the following prerequisite skills: A working knowledge of Secure Shell (SSH) and key exchange. Experience with the Unix Operating System, including Unix regular expressions. Familiarity with Tenable s Log Correlation Engine (LCE) operation and architecture as described in the Log Correlation Engine Administration and User Guide. Knowledge of general log formats from various operating systems, network devices and applications. This document is intended to be used with LCE installations for version 3.4 and higher. Standards and Conventions Throughout the documentation, filenames, daemons and executables are indicated with a courier bold font such as gunzip, httpd and /etc/passwd. Command line options and keywords will also be printed with the courier bold font. Command line options may or may not include the command line prompt and output text from the results of the command. Often, the command being run will be boldfaced to indicate what the user typed. Below is an example running of the Unix pwd command. # pwd /opt/lce/ # Important notes and considerations are highlighted with this symbol and grey text boxes. Log Parsing and Normalization Architecture The LCE daemon, lced, receives entire log messages from SYSLOG messages or LCE clients. For example, the following log message could arrive at the LCE through one of the LCE s log parsing clients or have been sent via SYSLOG across the network directly: Jun 22 01:02:34 godzilla kernel: eth1: Setting promiscuous mode. Normalization When the LCE receives these logs, it uses libraries (known as.prm files) to analyze the message. The first part of analysis is to recognize the message type with unique keywords. Copyright , Tenable Network Security, Inc. 3

4 Once a message type is recognized, it is normalized and relevant data is populated into an event schema. Type abuse access-denied application backdoor blacklist compliance compromise connection correlated database data-leak detected-change dhcp dns Description Events and logs dealing with access to pornography, illegal content and other types of network usage against policy. Events from devices that indicate that access was prevented, but did not necessarily require a login. For example, many web sites have content that might deny access to a non-logged in users. Generic logs from applications not specifically given their own types like ftp, database, web or mail. Any type of IDS or system log that indicates the presence of or probing for a known backdoor or Trojan. Logs generated by TASL correlation scripts that compare connection event types as well as network sessions with known lists of hostile IP networks. Events that track compliance standards such as PCI DSS and SOX. Logs that indicate IDS and system logs showing sever attacks. These are high-priority attacks that have been detected. For example, a Snort administrator access attempt or a system log that indicated that a known attack had occurred would both be normalized to this type. Any log from a web proxy, firewall, load balancer or other type of network device that logs a successful network connection event. There are a variety of TASL scripts that look for common types of network abuse, successful attacks and compromised systems. These alerts are categorized under the correlated type. Examples include successful password guessing and detection of systems that have had a worm outbreak. Logs from MySQL, MS-SQL, Oracle and other types of databases. Any event that indicates data leakage. These events originate from commercial data leakage vendors. Logs that indicate the network, system or users have somehow changed. Examples include changing a user s access rights as well as new hosts being added to the network. These logs originate from a variety of DHCP servers. These logs originate from a variety of DNS servers. Copyright , Tenable Network Security, Inc. 4

5 dos error firewall ftp games hids honeypot intrusion lce login login-failure logout mail nbad nbs All network IDS logs that indicate a denial of service attack are normalized with this type. Logs from a variety of applications, network devices and communications logs that also indicate some sort of resource attack are also normalized as dos type events. Any log from a system, application or log that indicates some sort of error condition is logged to this type. This can include errors from user input, hardware errors and many other types of logs. Any firewall log that has occurred from preventing access is tagged as a firewall event. For example, if an internal host was prevented from connecting to the outside world, it would be normalized as a firewall event. If a firewall allowed the connection, it would be logged as a connection event. Any logs from FTP servers that are not actual login or login-failure events. These include files and directories accessed as well as file transfers. Any logs from network monitoring applications such as NIDS that indicate the occurrence or presence of Internet and LAN games. Any logs from host based IDS systems that are distinct from antivirus systems. Any logs from commercial or open source honeypots that indicate connections from other networks. Logs from network IDS and systems that indicate intrusion events that are probes or likely non-compromise types of events. Any logs from the Log Correlation Engine clients about their status and overall CPU, storage and memory information about the systems they are connected to. For Windows systems, this also includes USB inserts and deletes. Any successful login event. These can come from servers, network events and applications. Any unsuccessful login event. These can come from servers, network events and applications. Some applications and systems also log when a user logs out of a system. Logs from Sendmail, Exchange, Postfix and many other types of servers that indicate receptions of and sending of . Logs from commercial network based anomaly systems. Any type of log that has never been seen before. There is a TASL script that keeps track of every local system and every log that has Copyright , Tenable Network Security, Inc. 5

6 ever occurred for it. If a new event occurs on a host, the LCE will alert if this has never occurred in the past. nessus network p2p-activity phishing process Any log from the Nessus vulnerability scanner except for remote connection events that are normalized to login or login-failure events. Any log from the Tenable Network Monitor or Tenable NetFlow Monitor or their post-processed events. Both of these LCE clients log network sessions and multiple TASL scripts further analyze these logs to generate logs for large bandwidth connections as well as connections lasting longer than 15 minutes. Any network monitoring application such as a NIDS that indicates the occurrence of P2P traffic such as LimeWire or Bittorrent. Any logs, such as those from an SPAM appliance, that indicates phishing activity. Any Windows or Unix program execution event. It includes hourly and daily summaries of program executions. This information comes from the process accounting logs in Unix and Audit process tracking on Windows. This category is supplemented by a TASL script (program_accounting.tasl), which generates a list of all programs being run on an hourly and daily per-system basis and also a daily list of programs per user. pup-activity radius reboot router SC3 scanning shutdown Any logs from system or network applications that indicate the presence of potentially unwanted software. Any authentication logs from Radius servers. Any type of log from a system, application or network device that indicates it has restarted. Any log from a variety of routers that indicates something has been done to the current system. For example, a router that logs changes to the OSPF routing table would be classified under this type. Any logs from the Security Center such as scan launches, additions of new users, deletion of reports and much more. Any type of log that indicates port scanning or port sweeping events. These logs can originate from many different sources including the Passive Vulnerability Scanner, network IDSes, firewalls and host-based applications. Any log that indicates a network device, operating system or application has been turned off. Copyright , Tenable Network Security, Inc. 6

7 spam startup stats switch system usb user-activity version virus vmware vpn vulnerability web web-error wireless Any logs, such as those from an SPAM appliance, that indicates the attempt to send a SPAM . Any log that indicates a network device, operating system or application has been started. Any logs generated by the LCE stats daemon that indicate large spikes in activity on a per-type basis. For example, the stats daemon will automatically alert when there has been a spike in login-failures. Any log from a variety of switches that indicates something has been done to the current system. For example, a switch that logs changes to its local configuration would be classified under this type. Any log from a router, switch or operating system that indicates some sort of activity. For example, a Red Hat Linux server running the up2date command would have the logs from that activity classified as a system type. Tracks the insert and remove events generated by LCE Windows agents when they detect drive insertion and removal. Any log from a router, switch or operating system that indicates some sort of activity. Any log from any device, application or system that can help identify the actual running version. Any log from host based anti-virus applications or network based IDS systems that indicate the occurrence or presence of virus activity. Any logs from VMware based applications. Logs from operating system, appliance based and firewall based VPNs. Any log that indicates the presence of a vulnerability. All web server logs, as well as web proxy logs that indicate some form of successful web access. All web server logs that indicate some form of web access that has resulted in an error such as 400 and 500 style HTTP codes. Any logs from wireless access devices. Below is an example screen capture of events as shown in a Security Center for a 24 hour period: Copyright , Tenable Network Security, Inc. 7

8 This portion of events (the screen image only shows SC3 types through lce types for 24 hours) offers some interesting patterns. The dark areas represent 6:00 PM through 6:00 AM. The activity graph shows that some types of events occur all the time, such as the intrusion types and lce types. If a Security Center user where to mouse over the graphs, they would be shown a pop up image of the total amount of events at that point and the exact times. Clicking on any of the event counts would bring the user to a list of unique events. For example, clicking on the 23 next to the SC3 type would show: This similar display displays the specific different set of normalized events that are part of the SC3 type. Event Schema Copyright , Tenable Network Security, Inc. 8

9 Every normalized event will attempt to populate as much of the following schema as possible: Source and destination IP addresses IP Protocol Source and Destination Ports Unique Event Name Unique Event Type Sensor name Time of Event User Name For example, the above promiscuous mode message is parsed by the LCE rule number The rule is shown below: id=1316 name=promiscuous mode enabled. match= kernel: match=: Promiscuous mode enabled. log=event:linux-promiscuous_mode_enabled type:system If this rule matches an event, it will populate the schema with the source IP of either the original SYSLOG message or the LCE client. It will also set an event name of Linux- Promiscuous_Mode_Enabled and an event type of system. This is an extremely simple normalization rule. This document will provide several examples that normalize similar log messages as well as more complex log messages such as firewall and intrusion detection logs. Libraries The LCE daemon references the.prm libraries located in the /opt/lce/daemons/plugins directory. The location of the directory used by LCE is controlled in the lce.conf file and may be located in other places if configured as such by the LCE administrator. Each library contains one or more LCE plugins that are designed to parse specific types of log files. The libraries may also contain specific information about the devices they support. For example, the library that parses certain types of Windows security events may contain information on how the Windows LCE Client should be configured. Missing Events It is quite likely that the LCE will receive logs for events but not have a rule designed to parse those events. The LCE is designed to only normalize what it has been told how to normalize. If configured to do so, through a setting in the lce.conf file, the LCE daemon will log any missing event to a file named notmatched.txt. This can be configured to keep the last 10,000 log events (which can be configured to be much higher if desired) and is useful for an immediate listing of what types of log events are being missed by the LCE. Copyright , Tenable Network Security, Inc. 9

10 Through analysis of the contents of this log, users can see what the actual log messages look like and modify their.prm libraries accordingly. Matching Multiple Events The LCE can also be configured (via the lce.conf file) to continue to parse each log message across the entire.prm library of plugins. This is useful if more than one plugin is destined for a specific type of log file. For example, for a firewall that performs network address translation, each log may have three IP addresses. One IP address will be the internal address, another would be the public address and the third would be an Internet address. A university may have their students on a private network such as , translate them to a public university IP address and finally log the fact that they downloaded their from Google s web site. By allowing the LCE to parse the same log multiple times, multiple events can be logged. More examples for the reason why multiple log hits would be required could be: Separate rules to parse web logs for valid/invalid web hits as well as performing IDS analysis of the URLs for suspicious attacks Separate rules for generic firewall accept/deny as well as matching on specific denied ports Separate rules for valid/invalid logins as well as alerting on specific user names such as root and administrator Force Sensor Name for Events In many cases, by the time syslog data reaches the LCE, the true source of the UDP packet is lost because of packet modification by intermediary forwarding systems. Because of this, LCE may inadvertently normalize data with a sensor name that does not truly match the originating system. To remediate this, a sensor named can be assigned to each IP address sending data to the LCE. This sensor name will be associated with all logs from the designated source, regardless of whether or not another sensor name is extracted from the log text. The configuration option is syslog-sensors-file and uses the following format: syslog-sensors-file /opt/lce/admin/syslog_sensors.txt The format of the syslog_sensors.txt file would be similar to the format below: CiscoPIX Corporate FW# CiscoPIX Corporate FW# CiscoPIX Corporate FW#3 Column one indicates the IP address obtained from the syslog packet, while column two indicates the desired sensor name. Searching Log Data from the Command-line Starting in LCE 3.2, LCE data may now be searched quickly and efficiently from the command-line. This functionality allows for programmatic searches of data and extends the power of LCE beyond the Security Center graphical user interface. Copyright , Tenable Network Security, Inc. 10

11 In order to search the compressed log archive data, a command-line search utility is provided: /opt/lce/search_logs The command-line format for a search is: # /opt/lce/search_logs <max results> <start date> <end date> <boolean expression> The <start date> and <end date> parameters must be in the form YYYY-MM-DD. The <max results> parameter indicates the maximum number of results to display. The search will terminate when this many results have been found, or when all logs within the provided date range have been searched (whichever comes first). Boolean expressions are described in the note below. For example, the following command provides the first 25 logs stored between January 1, 2001 and January 1, 2010 that contain the term illegal : # /opt/lce/search_logs illegal The output of the utility is in the form: <matching log event 1>... <matching log event N> When no results are found, the output is blank. A search with no matching results is expected to complete very quickly (the lazy evaluation is most efficient when negation is not used), while the time required for a search with results is a function of the amount of data being searched. For example, in order to complete a search for a month of data, all compressed logs from the month, perhaps several gigabytes, must potentially be read from disk. The only other possibility is that the archive data contains at least <max results> results, allowing the search to terminate when this number is reached. Writing Log Correlation Engine Plugins Log Correlation Engine Database Events Tenable s LCE is designed to receive log messages, parse out relevant fields of those log messages and then store the results in a proprietary database. Each entry stored in the database is known as a LCE event and contains the following fields: srcip - the source IP address of the event dstip - the destination IP address of the event srcport - the source port of the event dstport - the destination port of the event proto - the protocol of the event sensor - the name of the sensor that sent the event event - the actual event name type - the type of sensor that sent the event (IDS, firewall, etc.) Copyright , Tenable Network Security, Inc. 11

12 message - the full log message that triggered the storing of this event user name the actual login name used for the matching user An event stored in the database may not have all of these fields set. The number of the fields that are set depends on how much information was parsed and recorded by the LCE when receiving each log message. At a minimum, the event name and message fields should always be set. Log Correlation Engine Plugin Keywords There are several keywords available for writing plugins for the LCE. Some of these keywords are mandatory and some are optional. Keyword name=<plugin name> match=<match> Description This keyword specifies the name of the plugin. The name of the plugin generally describes what sort of log event this plugin is designed to trigger on. Multiple LCE plugins may have the same name. Match strings have the following format: [!]string! : Means that the packet must NOT match <string> A plugin may have multiple match statements. Here is a full example for a Snort ICMP event: match=snort: match=-> match={icmp} regex=<regex> This keyword specifies a complex regular expression search rule that will be applied to the log message. A regex is applied only after a log message has matched all of the match= patterns. For example: match=snort: match=-> match={icmp} regex=snort:.+\] ([a-za-z0-9_ \.]+) \[.*\{ICMP\} ([0-9]+(\.[0-9]+){3}) -> ([0-9]+(\.[0-9]+){3}) Parentheses are used in this regular expression to allow the LCE to remember and save matched patterns in a received log message. These matched patterns are generally the fields of the log message that you want to save in an event structure. If the above regex was applied against the following Snort ICMP alert, then the following fields of the log message would be saved Copyright , Tenable Network Security, Inc. 12

13 because of the presence of parenthesis in the regex rule: SYSLOG alert: <33>Mar 24 08:01:33 fwall snort: [1:483:2] ICMP PING CyberKit 2.2 Windows [Classification: Misc activity] [Priority: 3]: {ICMP} > Saved patterns: "ICMP PING CyberKit 2.2 Windows", " ", " " These matched patterns may be recalled using dollar sign notation to indicate which match we are referring to. These are of the forms $[0-9] where the digit 0-9 specifies which pattern (in the order each pattern was matched) to recall. So for the above example, each pattern could be recalled resulting in these matches: $1 - which recalls "ICMP PING CyberKit 2.2 Windows" $2 - which recalls " " $4 - which recalls " " Notice that the destination IP address is recalled using $4 and not $3. This is because each IP address regex pattern actually contains two sets of parenthesis: ([0-9]+(\.[0-9]+){3}) The first set of parenthesis, which are the outer parenthesis, match on the IP address as a whole. The second set of parenthesis, which are the inner parenthesis match on the last three octets of the IP address. Thus, this IP address regular expression results in two saved patterns. It just happens that in this case, we are only interested in the first of these saved patterns (the IP address as a whole). A match statement OR a regex is required. A plugin may contain multiple match statements but only one regex statement. log=<log options> The log keyword provides a way to specify what information to store in the LCE database if this plugin matches a received log message. As stated earlier, each entry stored in the LCE database is stored as a LCE event structure. The log keyword enables one to set each field of a stored event to either a value extracted from the received log message (using the saved patterns from the regex rule) or to a hard coded value written explicitly in the log statement. In this way a person can Copyright , Tenable Network Security, Inc. 13

14 save only those pieces of a log message that are useful. For example, the regex rule may specify a search rule for an IP address pattern. If this search rule matches an IP address in a received log message, then the log keyword allows one to specify whether the IP address should map to the source IP or the destination IP when storing the event for this message. Mapping may be done for each field in an event structure using the following keywords: srcip, dstip, proto, event, type,user and sensor. The syntax for each mapping is as follows: keyword:<value> Where keyword is one of srcip, dstip, proto, event, type, user or sensor and <value> is either written explicitly or is a reference to a saved match pattern from the regex rule. For example, suppose we had the following set of match patterns and regex rules designed to match a Snort ICMP event: match=snort: match=-> match={icmp} regex=snort:.+\] ([a-za-z0-9_ \.]+) \[.*\{ICMP\} ([0-9]+(\.[0-9]+){3}) -> ([0-9]+(\.[0-9]+){3}) An example Snort event that we would match on in this case is: <33>Mar 24 08:01:33 fwall snort: [1:483:2] ICMP PING CyberKit 2.2 Windows [Classification: Misc activity] [Priority: 3]: {ICMP} > Here the regex contains parenthesis so as to save the event name and source and destination IP addresses from this field. In order to store this event to the LCE database, we could set up the following log options: log=srcip:$2 dstip:$4 proto:1 event:snort_icmp_event type:ids Here the event name and protocol are hard-coded and the rest of fields are based on extracted patterns from the received log message as specified by the regex rule. Note that if a value is hard coded it may NOT contain spaces. So in the above log rule, event:snort_icmp_event could NOT have been written as event:snort ICMP event. Only the event mapping must be specified when writing a plugin. The rest of the mappings are optional. If no dstip mapping is specified, then by default the LCE will set the destination IP Copyright , Tenable Network Security, Inc. 14

15 address of an event to the address of the machine it received the log message from. All other mappings are zero-valued if not specified in the log rule. The log keyword is always required and within the log statement, the event keyword (e.g.: event:snort_tcp_event ) is required as well. User Tracking The LCE can be used to track the IP addresses a network user is originating from and then tag any other events from that IP address as belonging to that user. To make use of this, the LCE needs to know which types of logs in your organization contain the username you wish to correlate and track IP addresses from. Please refer to the LCE Administraion and User Guide to learn how to configure this. When the LCE is configured, it will only use PRM IDs that have been configured to process user to IP address relationships. Consider the following PRM from the auth_bluesocket.prm file: id=1032 name=the BlueSocket device had a network user start their network session. match=user_tracking: match=event=user_l match=event=user_login_successful match=obj=user regex=&ipaddr=([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)&name=(.*)&msg= log= type:login event:bluesocket-user_login srcip:$1 user:$2 An actual user authentication message for BlueSocket looks like this: <181>user_tracking: event=user_login_successful&loglevel=notice&obj=user&ipaddr= &name=user1@nessus.org&msg=login RADIUS user user1@nessus.org on Primary RADIUS server at [00:13:02:89:d1:f5]/ as role Authenticated, login time = :39:29, sessionid = 00:0E:0C:73:A4:E0: & The regex and log statements in the PRM extracts the string and assigns it to srcip, and the username is assigned user1@nessus.org. If the LCE has not been configured to process ID 1032 as a source of user to IP address tracking, the event is normalized and logged as any other event. However, if ID 1032 were enabled for user to IP tracking, the LCE would perform the following steps: It would check the current table of usernames. If this were a new user, an additional new user event would be generated. It would also check the current table of usernames and IP address matches. If this were a new IP address for an existing user, then a new user to IP address message would be generated. Copyright , Tenable Network Security, Inc. 15

16 Lastly, for any other events originating from the IP address of this login (in this case ) they would all be automatically assigned a username of user1@nessus.org. Log Correlation Engine Plugin Management The LCE is distributed with a large number of plugins, but they may not all be of interest in a particular environment. To improve performance and facilitate log analysis, configure the LCE server with only the plugins desired for analysis. To disable a plugin, edit the file /opt/lce/admin/disabled-prms.txt and add in the full name of the PRM you wish to be ignored and then restart the LCE. Desired libraries, modified libraries and custom plugins should be placed in a separate plugins directory and the lce.conf file can be configured to direct the lced process to pull its events from this new directory. Modifying Tenable PRM files is not recommended, as any update process will overwrite them with subsequent changes made by Tenable. Log Correlation Engine Clients There are a number of LCE clients available for a variety of events and operating systems. They are all roughly configured the same way in that they are pointed to a data source, and they are connected to the LCE server by specifying the IP addresses and shared secret. Each LCE client must have the corresponding shared secret key specified in the LCE server s lce.conf file. Each of the available LCE clients are covered in a separate document entitled LCE Client Guide. For More Information Tenable has produced a variety of other documents detailing the LCE s deployment, configuration, user operation and overall testing. These are listed here: Log Correlation Engine Administration and User Guide additional information for installing, configuring and operating the LCE Log Correlation Engine Client Guide how to configure, operate and manage the various Unix, Windows, netflow, OPSEC and other clients TASL Reference Guide explanation of the Tenable Application Scripting Language with extensive examples of a variety of correlation rules Log Correlation Engine Statistics Daemon Guide configuration, operation and theory of the LCE s statistic daemon used to discover behavioral anomalies Documentation is also available for Nessus, the Passive Vulnerability Scanner and the Security Center. Please feel free to contact us at support@tenable.com, sales@tenable.com or visit our web site at Copyright , Tenable Network Security, Inc. 16

17 About Tenable Network Security Tenable, headquartered in Columbia, Md., USA, is the world leader in Unified Security Monitoring. Tenable provides agent-less solutions for continuous monitoring of vulnerabilities, configurations, data leakage, log analysis and compromise detection. For more information, please visit us at TENABLE Network Security, Inc Columbia Gateway Drive Suite 100 Columbia, MD TEL: Copyright , Tenable Network Security, Inc. 17