Система и протокол сетевой регистрации событий (Syslog)

Network event logging system and protocol

In computing, syslog /'//s//ɪ//s//l//ɒ//g/ is a standard for message logging. It allows separation of the software that generates messages, the system that stores them, and the software that reports and analyzes them. Each message is labeled with a facility code, indicating the type of system generating the message, and is assigned a severity level. Computer system designers may use syslog for system management and security auditing as well as general informational, analysis, and debugging messages. A wide variety of devices, such as printers, routers, and message receivers across many platforms use the syslog standard. This permits the consolidation of logging data from different types of systems in a central repository. Implementations of syslog exist for many operating systems. When operating over a network, syslog uses a client server architecture where a syslog server listens for and logs messages coming from clients.

Syslog was developed in the 1980s by Eric Allman as part of the Sendmail project. It was readily adopted by other applications and has since become the standard logging solution on Unix like systems. A variety of implementations also exist on other operating systems and it is commonly found in network devices, such as routers. Syslog originally functioned as a de facto standard, without any authoritative published specification, and many implementations existed, some of which were incompatible. The Internet Engineering Task Force documented the status quo in RFC 3164 in August of 2001. It was standardized by RFC 5424 in March of 2009. Various companies have attempted to claim patents for specific aspects of syslog implementations. This has had little effect on the use and standardization of the protocol.

The information provided by the originator of a syslog message includes the facility code and the severity level. The syslog software adds information to the information header before passing the entry to the syslog receiver. Such components include an originator process ID, a timestamp, and the hostname or IP address of the device.

A facility code is used to specify the type of system that is logging the message. Messages with different facilities may be handled differently. The list of facilities available is described by the standard:

When operating over a network, syslog uses a client server architecture where the server listens on a well known or registered port for protocol requests from clients. Historically the most common transport layer protocol for network logging has been User Datagram Protocol (UDP), with the server listening on port 514. Because UDP lacks congestion control mechanisms, Transmission Control Protocol (TCP) port 6514 is used; Transport Layer Security is also required in implementations and recommended for general use.

Since each process, application, and operating system was written independently, there is little uniformity to the payload of the log message. For this reason, no assumption is made about its formatting or contents. A syslog message is formatted (RFC 5424 gives the Augmented Backus–Naur form (ABNF) definition), but its MSG field is not. The network protocol is simplex communication, with no means of acknowledging the delivery to the originator.

Various groups are working on draft standards detailing the use of syslog for more than just network and security event logging, such as its proposed application within the healthcare environment. Regulations, such as the Sarbanes–Oxley Act, PCI DSS, HIPAA, and many others, require organizations to implement comprehensive security measures, which often include collecting and analyzing logs from many different sources. The syslog format has proven effective in consolidating logs, as there are many open source and proprietary tools for reporting and analysis of these logs. Utilities exist for conversion from Windows Event Log and other log formats to syslog. Managed Security Service Providers attempt to apply analytical techniques and artificial intelligence algorithms to detect patterns and alert customers to problems.