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Printable Version: RFC2196.PDF
RFC 2196 Site Security Handbook September 1997 4.6.2 Collection Process The collection process should be enacted by the host or resource being accessed. Depending on the importance of the data and the need to have it local in instances in which services are being denied, data could be kept local to the resource until needed or be transmitted to storage after each event. There are basically three ways to store audit records: in a read/write file on a host, on a write-once/read-many device (e.g., a CD-ROM or a specially configured tape drive), or on a write-only device (e.g., a line printer). Each method has advantages and disadvantages. File system logging is the least resource intensive of the three methods and the easiest to configure. It allows instant access to the records for analysis, which may be important if an attack is in progress. File system logging is also the least reliable method. If the logging host has been compromised, the file system is usually the first thing to go; an intruder could easily cover up traces of the intrusion. Collecting audit data on a write-once device is slightly more effort to configure than a simple file, but it has the significant advantage of greatly increased security because an intruder could not alter the data showing that an intrusion has occurred. The disadvantage of this method is the need to maintain a supply of storage media and the cost of that media. Also, the data may not be instantly available. Line printer logging is useful in system where permanent and immediate logs are required. A real time system is an example of this, where the exact point of a failure or attack must be recorded. A laser printer, or other device which buffers data (e.g., a print server), may suffer from lost data if buffers contain the needed data at a critical instant. The disadvantage of, literally, "paper trails" is the need to keep the printer fed and the need to scan records by hand. There is also the issue of where to store the, potentially, enormous volume of paper which may be generated. For each of the logging methods described, there is also the issue of securing the path between the device generating the log and actual logging device (i.e., the file server, tape/CD-ROM drive, printer). If that path is compromised, logging can be stopped or spoofed or both. In an ideal world, the logging device would be directly Fraser, Ed. Informational [Page 35]