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Security Compromise Underway?
By: Dave Wreski
Spotting a security compromise under way can be a tense undertaking. How you react can have large consequences.
If the compromise you are seeing is a physical one, odds are you have spotted someone who has broken into your home, office or lab. You should notify your local authorities. In a lab, you might have spotted someone trying to open a case or reboot a machine. Depending on your authority and procedures, you might ask them to stop, or contact your local security people.
If you have detected a local user trying to compromise your security, the first thing to do is confirm they are in fact who you think they are. Check the site they are logging in from. Is it the site they normally log in from? No? Then use a non-electronic means of getting in touch. For instance, call them on the phone or walk over to their office/house and talk to them. If they agree that they are on, you can ask them to explain what they were doing or tell them to cease doing it. If they are not on, and have no idea what you are talking about, odds are this incident requires further investigation. Look into such incidents , and have lots of information before making any accusations.
If you have detected a network compromise, the first thing to do (if you are able) is to disconnect your network. If they are connected via modem, unplug the modem cable; if they are connected via Ethernet, unplug the Ethernet cable. This will prevent them from doing any further damage, and they will probably see it as a network problem rather than detection.
If you are unable to disconnect the network (if you have a busy site, or you do not have physical control of your machines), the next best step is to use something like tcp_wrappers or ipfwadm to deny access from the intruder's site.
If you can't deny all people from the same site as the intruder, locking the user's account will have to do. Note that locking an account is not an easy thing. You have to keep in mind .rhosts files, FTP access, and a host of possible backdoors.
After you have done one of the above (disconnected the network, denied access from their site, and/or disabled their account), you need to kill all their user processes and log them off.
You should monitor your site well for the next few minutes, as the attacker will try to get back in. Perhaps using a different account, and/or from a different network address.
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 Mozilla packages fix several vulnerabilities | ||
| 20th, October, 2005
Updated package. advisories/debian/debian-new-mozilla-packages-fix-several-vulnerabilities-49307 |
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| Debian: New module-assistant package fixes insecure temporary file | ||
| 20th, October, 2005
Updated package. advisories/debian/debian-new-module-assistant-package-fixes-insecure-temporary-file |
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| Debian: New Mozilla Thunderbird packages fix several vulnerabilities | ||
| 20th, October, 2005
Updated package. advisories/debian/debian-new-mozilla-thunderbird-packages-fix-several-vulnerabilities-8356 |
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| Debian: New eric packages fix arbitrary code execution | ||
| 21st, October, 2005
Updated Package. advisories/debian/debian-new-eric-packages-fix-arbitrary-code-execution |
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| Debian: New sudo packages fix arbitrary command execution | ||
| 25th, October, 2005
Updated package. advisories/debian/debian-new-sudo-packages-fix-arbitrary-command-execution |
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| Debian: New libgda2 packages fix arbitrary code execution | ||
| 25th, October, 2005
Updated package. advisories/debian/debian-new-libgda2-packages-fix-arbitrary-code-execution-77320 |
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| Debian: New libgda2 packages fix arbitrary code execution | ||
| 25th, October, 2005
Updated package. advisories/debian/debian-new-libgda2-packages-fix-arbitrary-code-execution-77320 |
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| Debian: New imlib packages fix arbitrary code execution | ||
| 26th, October, 2005
Upgrade package. advisories/debian/debian-new-imlib-packages-fix-arbitrary-code-execution |
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| Debian: New koffice packages fix arbitrary code execution | ||
| 26th, October, 2005
Upgraded package. advisories/debian/debian-new-koffice-packages-fix-arbitrary-code-execution-12906 |
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| Debian: New net-snmp packages fix denial of service | ||
| 26th, October, 2005
Updated package. advisories/debian/debian-new-net-snmp-packages-fix-denial-of-service |
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| Debian: New lynx packages fix arbitrary code execution | ||
| 27th, October, 2005
Updated package. advisories/debian/debian-new-lynx-packages-fix-arbitrary-code-execution |
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| Debian: New OpenSSL packages fix cryptographic weakness | ||
| 27th, October, 2005
Updated package. advisories/debian/debian-new-openssl-packages-fix-cryptographic-weakness-46955 |
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| Gentoo | ||
| Gentoo: AbiWord New RTF import buffer overflows | ||
| 20th, October, 2005
AbiWord is vulnerable to an additional set of buffer overflows during RTF import, making it vulnerable to the execution of arbitrary code. |
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| Gentoo: Netpbm Buffer overflow in pnmtopng | ||
| 20th, October, 2005
The pnmtopng utility, part of the Netpbm tools, contains a vulnerability which can potentially result in the execution of arbitrary code. |
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| Gentoo: cURL NTLM username stack overflow | ||
| 22nd, October, 2005
cURL is vulnerable to a buffer overflow which could lead to the execution of arbitrary code. |
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| Gentoo: Zope File inclusion through RestructuredText | ||
| 25th, October, 2005
Zope is vulnerable to a file inclusion vulnerability when exposing RestructuredText functionalities to untrusted users. |
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| Gentoo: phpMyAdmin Local file inclusion and XSS vulnerabilities | ||
| 25th, October, 2005
phpMyAdmin contains a local file inclusion vulnerability that may lead to the execution of arbitrary code, along with several cross-site scripting issues. |
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| Red Hat | ||
| RedHat: Moderate: ethereal security update | ||
| 25th, October, 2005
Updated Ethereal packages that fix various security vulnerabilities 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-ethereal-security-update-43419 |
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| RedHat: Low: pam security update | ||
| 26th, October, 2005
An updated pam package that fixes a security weakness is now available for Red Hat Enterprise Linux 4. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-pam-security-update-RHSA-2005-805-01 |
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| RedHat: Low: fetchmail security update | ||
| 26th, October, 2005
Updated fetchmail packages that fix insecure configuration file creation 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-fetchmail-security-update-RHSA-2005-823-01 |
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