Analyzing a Log File
| | |
| ||
| ||
Collecting security audit messages in the security audit log file is useless without periodically reviewing it for suspicious activity. You use the Audit Analysis utility (ANALYZE/AUDIT) to examine the data in the security audit log file.
ANALYZE/AUDIT generates a report from the log file so that you become familiar with normal activity on your system and can easily spot atypical activity. It summarizes events for you and plots where activity is occurring on the cluster. The utility also helps you analyze atypical activity because it is capable of selecting a subset of information from an audit report and of providing fuller information for your analysis. While the analysis of a single audit log file might not be significant, audit records can, over time, reveal a pattern of activity that indicates security violations.
This section describes how to analyze audit log files on your system. Although the way you use ANALYZE/AUDIT depends upon the security needs at your site, there are a number of common steps that you should follow, regardless of the extent to which you use the utility. Before you can recognize potential security problems, you need to become familiar with the normal operation of your system. Then you can develop a procedure for generating and reviewing audit reports on a periodic basis. Whenever your regular analysis of audit log files leads you to suspect a security problem, you should perform a detailed investigation of selected security events.
Step 1: Know What Is Normal
As a security administrator, you should be able to answer the following questions before analyzing an audit log file:
What are the typical hours of operation for most users of the system?
Are there specific users who normally operate with advanced privileges?
Which images generate system security events as part of other applications?
Are there any regular batch or network jobs that run at specific times of the day?
By knowing the answers to these questions, you can eliminate false alarms, which otherwise may cause you to wrongly suspect a security problem.
Step 2: Periodically Analyze the Audit Report
The most common type of report to generate is a brief, daily listing of events. You can create a command procedure that runs in a batch job every evening before midnight to generate a report of the day's security event messages. (You can use the same procedure to create a new version of the audit log [see “Maintaining the File”].)
The following example shows the ANALYZE/AUDIT command line to generate this report:
|
|
|
|
|
|
The first command in this example produces an audit report named 31DEC2000.AUDIT, which contains one-line descriptions of all the security event messages generated during the current day.
The second command mails the file to the security administrator for examination.
Depending on the number of security events that you are auditing on your system, it can be impractical to review every audit record written to the audit log file. In this case, you can select a specific set of records from the log file, such as all audit records related to changes in the authorization database and break-in attempts, or all events occurring outside normal business hours.
Analyze any subprocess-related audits with the knowledge that a pipe subprocess (created by the DCL PIPE command) can generate the audits. The PIPE command can create a large number of subprocesses to execute a single PIPE command. This can mean a potential increase in auditing events that are related to subprocess activities (for example, process creation, process deletion, login, logfailure, and logout).
It is important that you review audit reports as soon as possible. The sooner you inspect the reports, the sooner you become aware of any possible breach of security on the system and can determine the extent of the problem. You can make the inspection of the previous day's audit report a regular part of your morning routine, or you can create a program that reviews the report and notifies you through the Mail utility (MAIL) when suspicious events appear.
Step 3: Scrutinize Suspicious Activity
If, during your review, you find any security events that appear suspicious or out of place, like login attempts outside normal business hours, then use the Audit Analysis utility to perform a more detailed inspection of the security audit log file. A full report can help you determine which security events logged to the audit log file warrant a more thorough investigation.
The following command generates a full report of selected security audit records:
|
|
|
The audit report for December 31, 2000 contains information on all intrusion attempts and all modifications to the system user authorization file (SYSUAF.DAT) and the rights database (RIGHTSLIST.DAT).
The Audit Analysis utility is the tool you use to produce a meaningful report from a binary log file. This section and the sections that follow describe how to use the utility, but see the HP OpenVMS System Management Utilities Reference Manual for complete documentation of the utility's commands and qualifiers.
To invoke the Audit Analysis utility, use the following DCL command:
ANALYZE/AUDIT file-name
For the file-name parameter, substitute the name of the file from which audit reports are to be generated. The default name of the security audit log file is SECURITY.AUDIT$JOURNAL. You must specify the directory: SYS$MANAGER.
With the Audit Analysis utility, you are able to extract all or some of the security event messages from a single audit log and produce reports with various levels of detail.
The audit report reflects events from the set of event classes a site has enabled (see “Reporting Security-Relevant Events”). You can tailor the report so only a subset of events are extracted. The selection criteria can be based on time, on event class, or on field of data within the event message. (See the documentation of the /SELECT qualifier in the HP OpenVMS System Management Utilities Reference Manual.) “Qualifiers for the Audit Analysis Utility” summarizes the qualifiers that determine the content of the report.
Table 10-6 Qualifiers for the Audit Analysis Utility
| Type | Qualifier | Description |
|---|---|---|
Content | /BEFORE | Extracts event messages logged before the specified time. |
/SINCE | Extracts event messages logged after the specified of time. | |
/EVENT_TYPE | Extracts event messages of a specific event class (see “Kinds of Security Events the System Can Report” ). | |
/SELECT | Extracts event messages based on data in the messages. (For example, /SELECT=USERNAME=JSNOOP lists only security event messages generated by user JSNOOP.) | |
/IGNORE | Excludes event messages from the report based on data in the messages. | |
Format | /BRIEF | Produces a report with one line of information about each record in the audit log file, such as the type of event, when it occurred, and the terminal from which it originated (see “Brief Audit Report”). This is the default. |
/FULL | Provides all possible data for each record in the audit log file being processed (see “One Record from a Full Audit Report”). “Alarm Messages” provides sample alarm messages for each event class. | |
/SUMMARY | Lists the total number of audit messages for each event class in the log file being analyzed (see “Summary of Events in an Audit Log File”). It can also plot the aggregate events per hour on each node. | |
/BINARY | Produces a binary file so you can extract records for further analysis using your own data reduction tools. See the HP OpenVMS System Management Utilities Reference Manual for a description of the audit message record format. | |
Destination | /OUTPUT | Specifies the report destination. By default, it goes to SYS$OUTPUT. |
ANALYZE/AUDIT produces audit reports in different formats (see “Qualifiers for the Audit Analysis Utility”). The utility produces a one-line summary of each record in the log file by default. Brief, one-line reports are most useful for routine analysis of a log file. The more detailed full reports provide the detail necessary for analyzing records of a suspicious nature. If you are interested in archiving portions of a log file, the binary listing lets you store a subset of an audit log file.
A summary report helps you identify potential security problems quickly. For each class of security event, a summary report can list the total number of audit messages extracted from the security audit log file being analyzed. A summary report can also display a plot of auditing activity, based on the system generating the event message, the time when it occurred, and the total number of events seen.
“Brief Audit Report” shows a brief report of all the security audit events logged to the system security audit log file. In the ANALYZE/AUDIT command that generates the report, substitute the name of your audit log file.
Example 10-4 Brief Audit Report
|
|
|
|
|
|
“One Record from a Full Audit Report” shows one record from a full format audit report. In the ANALYZE/AUDIT command that generates the report, substitute the name of your audit log file.
Example 10-5 One Record from a Full Audit Report
|
|
|
|
|
|
“Summary of Events in an Audit Log File” shows a summary report. In the ANALYZE/AUDIT command that generates the report, substitute the name of your audit log file.
Example 10-6 Summary of Events in an Audit Log File
|
|
|
|
|
|
When you send output to a terminal, you can analyze an audit log file interactively. At any time during the display of a listing, you can interrupt the report being displayed by pressing Ctrl/C. This automatically initiates a full listing and gives you the Command> prompt. In command mode, you can advance or return to earlier records in the report and study them in greater detail.
At the Command> prompt, you can enter any of the ANALYZE/AUDIT commands listed in the HP OpenVMS System Management Utilities Reference Manual to modify the analysis criteria, to change position within the audit report, or to toggle between full and brief displays. To return to an audit report listing, enter the CONTINUE command.
When a routine analysis of an audit log file leads you to suspect that the security of your system has been compromised (through an actual or attempted intrusion, repeated login failures, or any other suspicious security events), you can investigate the source of the security event through a more detailed inspection of the security audit log file.
For example, assume that you see the security events shown in “Identifying Suspicious Activity in the Audit Report” during a routine inspection of the previous day's audit report.
Example 10-7 Identifying Suspicious Activity in the Audit Report
|
|
|
The security events displayed in the report shown in “Identifying Suspicious Activity in the Audit Report” indicate that user Kovacs logged in to the system following four unsuccessful login attempts. Shortly after logging in, user Kovacs created a new account in the system user authorization file (SYSUAF.DAT).
At this point, you must determine whether this behavior is normal or abnormal. Is user Kovacs authorized to add new user accounts to the system? If you believe that the security of your system has been compromised, use the following command to generate a more detailed report from the security audit log file to determine if damage has been done to your system:
|
|
|
The command in this example generates a full report of all security audit events written to the audit log file since user Kovacs first attempted to log in to the system. In a full format report, all the data for each record in the audit log file is displayed. Using the full report, you can determine the name of the remote user who logged in under the local KOVACS account and the node from which the login was made, as shown in “Scrutinizing a Suspicious Record”.
Example 10-8 Scrutinizing a Suspicious Record
|
|
|
The information displayed in “Scrutinizing a Suspicious Record” indicates that the login failures and subsequent successful login were made by user Follen from the remote node NACHWA. Your next step is to determine whether the security events were generated by user Follen or by someone who has broken into the remote node NACHWA through the FOLLEN account.