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System Accounting
Dave Wreski
Be sure to keep an eye on what gets written there, especially under the auth facility. Multiple login failures, for example, can indicate an attempted break-in.
Where to look for your log file will depend on your distribution. In a Linux system that conforms to the "Linux Filesystem Standard", such as Red Hat, you will want to look in /var/log and check messages, mail.log, and others.
You can find out where your distribution is logging to by looking at your /etc/syslog.conf file. This is the file that tells syslogd (the system logging daemon) where to log various messages.
You might also want to configure your log-rotating script or daemon to keep logs around longer so you have time to examine them. Take a look at the logrotate package on recent Red Hat distributions. Other distributions likely have a similar process.
If your log files have been tampered with, see if you can determine when the tampering started, and what sort of things appeared to be tampered with. Are there large periods of time that cannot be accounted for? Checking backup tapes (if you have any) for untampered log files is a good idea.
Intruders typically modify log files in order to cover their tracks, but they should still be checked for strange happenings. You may notice the intruder attempting to gain entrance, or exploit a program in order to obtain the root account. You might see log entries before the intruder has time to modify them.
You should also be sure to separate the auth facility from other log data, including attempts to switch users using su, login attempts, and other user accounting information.
If possible, configure syslog to send a copy of the most important data to a secure system. This will prevent an intruder from covering his tracks by deleting his login/su/ftp/etc attempts. See the syslog.conf man page, and refer to the @ option.
Finally, log files are much less useful when no one is reading them. Take some time out every once in a while to look over your log files, and get a feeling for what they look like on a normal day. Knowing this can help make unusual things stand out.
Read more from the Linux Security Howto:
/howtos
LinuxSecurity.com Feature Extras:
Linux File & Directory Permissions Mistakes - One common mistake Linux administrators make is having file and directory permissions that are far too liberal and allow access beyond that which is needed for proper system operations. A full explanation of unix file permissions is beyond the scope of this article, so I'll assume you are familiar with the usage of such tools as chmod, chown, and chgrp. If you'd like a refresher, one is available right here on linuxsecurity.com.
Introduction: Buffer Overflow Vulnerabilities - Buffer overflows are a leading type of security vulnerability. This paper explains what a buffer overflow is, how it can be exploited, and what countermeasures can be taken to prevent the use of buffer overflow vulnerabilities.
Getting to Know Linux Security: File Permissions - Welcome to the first tutorial in the 'Getting to Know Linux Security' series. The topic explored is Linux file permissions. It offers an easy to follow explanation of how to read permissions, and how to set them using chmod. This guide is intended for users new to Linux security, therefore very simple. If the feedback is good, I'll consider creating more complex guides for advanced users. Please let us know what you think and how these can be improved.
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Thank you for reading the LinuxSecurity.com weekly security newsletter. The purpose of this document is to provide our readers with a quick summary of each week's most relevant Linux security headline.
| Debian | ||
| Debian: New mason packages fix missing init script | ||
| 6th, October, 2005
Updated package. advisories/debian/debian-new-mason-packages-fix-missing-init-script |
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| Debian: New cpio packages fix several vulnerabilities | ||
| 7th, October, 2005
Updated package. advisories/debian/debian-new-cpio-packages-fix-several-vulnerabilities |
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| Debian: New dia packages fix arbitrary code execution | ||
| 8th, October, 2005
Updated package. advisories/debian/debian-new-dia-packages-fix-arbitrary-code-execution-40937 |
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| Debian: New masqmail packages fix several vulnerabilities | ||
| 8th, October, 2005
Updated package. advisories/debian/debian-new-masqmail-packages-fix-several-vulnerabilities |
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| Debian: New shorewall packages fix firewall bypass | ||
| 8th, October, 2005
Updated package. advisories/debian/debian-new-shorewall-packages-fix-firewall-bypass |
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| Debian: New tcpdump packages fix denial of service | ||
| 9th, October, 2005
Updated package. advisories/debian/debian-new-tcpdump-packages-fix-denial-of-service-57234 |
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| Debian: New openvpn packages fix denial of service | ||
| 9th, October, 2005
Updated package. advisories/debian/debian-new-openvpn-packages-fix-denial-of-service |
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| Debian: New up-imapproxy packages fix arbitrary code execution | ||
| 9th, October, 2005
Updated package. advisories/debian/debian-new-up-imapproxy-packages-fix-arbitrary-code-execution |
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| Debian: New ethereal packages fix several vulnerabilities | ||
| 9th, October, 2005
Updated package. advisories/debian/debian-new-ethereal-packages-fix-several-vulnerabilities-72520 |
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| Debian: New tcpdump packages fix denial of service | ||
| 9th, October, 2005
Updated package. advisories/debian/debian-new-tcpdump-packages-fix-denial-of-service-57234 |
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| Debian: New weex packages fix arbitrary code execution | ||
| 10th, October, 2005
Updated package. advisories/debian/debian-new-weex-packages-fix-arbitrary-code-execution |
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| Debian: New py2play packages fix arbitrary code execution | ||
| 10th, October, 2005
Updated package. advisories/debian/debian-new-py2play-packages-fix-arbitrary-code-execution |
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| Debian: New graphviz packages fix insecure temporary file | ||
| 10th, October, 2005
Updated package. advisories/debian/debian-new-graphviz-packages-fix-insecure-temporary-file |
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| Debian: New xloadimage packages fix arbitrary code execution | ||
| 10th, October, 2005
Updated package. advisories/debian/debian-new-xloadimage-packages-fix-arbitrary-code-execution |
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| Debian: New xli packages fix arbitrary code execution | ||
| 10th, October, 2005
Updated package. advisories/debian/debian-new-xli-packages-fix-arbitrary-code-execution |
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| Debian: New Ruby packages fix safety bypass | ||
| 11th, October, 2005
Updated package. advisories/debian/debian-new-ruby-packages-fix-safety-bypass |
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| Debian: New uw-imap packages fix arbitrary code execution | ||
| 11th, October, 2005
Updated package. advisories/debian/debian-new-uw-imap-packages-fix-arbitrary-code-execution |
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| Debian: New Ruby 1.6 packages fix safety bypass | ||
| 11th, October, 2005
Updated package. advisories/debian/debian-new-ruby-16-packages-fix-safety-bypass |
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| Debian: New xine-lib packages fix arbitrary code execution | ||
| 12th, October, 2005
Updated package. advisories/debian/debian-new-xine-lib-packages-fix-arbitrary-code-execution-5517 |
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| Debian: New Ruby 1.8 packages fix safety bypass | ||
| 13th, October, 2005
Updated package. advisories/debian/debian-new-ruby-18-packages-fix-safety-bypass |
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| Debian: New hylafax packages fix insecure temporary files | ||
| 13th, October, 2005
Updated package. advisories/debian/debian-new-hylafax-packages-fix-insecure-temporary-files |
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| Gentoo | ||
| Gentoo: Ruby Security bypass vulnerability | ||
| 6th, October, 2005
Ruby is vulnerable to a security bypass of the safe level mechanism. |
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| Gentoo: Dia Arbitrary code execution through SVG import | ||
| 6th, October, 2005
Improperly sanitised data in Dia allows remote attackers to execute arbitrary code. |
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| Gentoo: RealPlayer, Helix Player Format string vulnerability | ||
| 7th, October, 2005
RealPlayer and Helix Player are vulnerable to a format string vulnerability resulting in the execution of arbitrary code. |
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| Gentoo: xine-lib Format string vulnerability | ||
| 8th, October, 2005
xine-lib contains a format string error in CDDB response handling that may be exploited to execute arbitrary code. |
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| Gentoo: Weex Format string vulnerability | ||
| 8th, October, 2005
Weex contains a format string error that may be exploited by malicious servers to execute arbitrary code. |
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| Gentoo: uw-imap Remote buffer overflow | ||
| 11th, October, 2005
uw-imap is vulnerable to remote overflow of a buffer in the IMAP server leading to execution of arbitrary code. |
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| Gentoo: OpenSSL SSL 2.0 protocol rollback | ||
| 12th, October, 2005
When using a specific option, OpenSSL can be forced to fallback to the less secure SSL 2.0 protocol. |
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| Red Hat | ||
| RedHat: Important: thunderbird security update | ||
| 6th, October, 2005
An updated thunderbird package that fixes various bugs is now available for Red Hat Enterprise Linux 4. This update has been rated as having important security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-important-thunderbird-security-update-66245 |
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| RedHat: Low: binutils security update | ||
| 11th, October, 2005
An updated binutils package that fixes minor security issues is now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-binutils-security-update-37292 |
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| RedHat: Low: libuser security update | ||
| 11th, October, 2005
Updated libuser packages that fix various security issues are now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-libuser-security-update-RHSA-2005-770-01 |
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| RedHat: Moderate: util-linux and mount security update | ||
| 11th, October, 2005
Updated util-linux and mount packages that fix two security issues are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-util-linux-and-mount-security-update-RHSA-2005-782-01 |
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| RedHat: Moderate: ruby security update | ||
| 11th, October, 2005
Updated ruby packages that fix an arbitrary command execution issue are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-ruby-security-update-81302 |
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| RedHat: Moderate: openssl security update | ||
| 11th, October, 2005
Updated OpenSSL packages that fix various security issues are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-openssl-security-update-13800 |
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