Linux malware

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The Linux operating system, Unix and other Unix-like computer operating systems are generally regarded as well-protected against computer viruses.^[1]

There has not yet been a single widespread Linux malware threat of the type that Microsoft Windows software currently faces; this is commonly attributed to the malware's lack of root access and fast updates to most Linux vulnerabilities.^[2]

The number of malicious programs—including viruses, Trojans, and other threats—specifically written for Linux has been on the increase in recent years and more than doubled during 2005 from 422 to 863.^[3]

Contents 1 Linux vulnerability 1.1 Viruses and trojan horses 1.2 Worms and targeted attacks 1.3 WWW scripts 1.4 Cross-platform viruses 2 Anti-virus applications 3 Threats 3.1 Trojans 3.2 Viruses 3.3 Worms 4 See also 5 References 6 External links

[edit] Linux vulnerability

Like Unix systems, Linux implements a multi-user environment where users are granted specific privileges and there is some form of access control implemented. To gain control over a Linux system or cause any serious consequence to the system itself, the malware would have to gain root access to the system.^[2]

Shane Coursen, a senior technical consultant with Kaspersky Lab noted, "The growth in Linux malware is simply due to its increasing popularity, particularly as a desktop operating system ... The use of an operating system is directly correlated to the interest by the malware writers to develop malware for that OS."^[3]

[edit] Viruses and trojan horses

The viruses listed below pose a potential, although minimal, threat to Linux systems. If an infected binary containing one of the viruses were run, the system would be infected. The infection level would depend on which user with what privileges ran the binary. A binary run under the root account would be able to infect the entire system. Privilege escalation vulnerabilities may permit malware running under a limited account to infect the entire system.

It is worth noting that this is true for any malicious program that is run without special steps taken to limit its privilegies. It is trivial to add a code snippet to any program that a user may download and let this additional code download a modified login server, an open mail relay or similar and make this additional component run any time the user logs in. No special malware writing skills are needed for this. Special skill may be needed for tricking the user to run the (trojan) program in the first place.

The use of software repositories significantly reduces any threat of installation of malware, as the software repositories are checked by maintainers, who try to ensure that their repository is malware-free. Subsequently, to ensure safe distribution of the software, md5 checksums are made available. These make it possible to reveal modified versions that may have been introduced by e.g. hijacking of communications using a man-in-the-middle attack or via a redirection attack such as ARP or DNS poisoning. Careful use of these digital signatures provides an additional line of defense, which limits the scope of attacks to include only the original authors, package and release maintainers and possibly others with suitable administrative access, depending on how the keys and checksums are handled.

Vulnerability to trojan horses and viruses is thus about users willing to run code from sources that should not be trusted and to some extent about distributions not by default checking the authencity of software downloaded while a system was the target of an attack.

[edit] Worms and targeted attacks

The classical threat to Unix-like systems is vulnerabilities in network daemons, such as ssh and WWW servers. These can be used by worms or for attacks against specific targets. As servers are patched quite quickly when a vulnerability is found, there have been only a few widespread worms of this kind. As specific targets can be attacked through a vulnerability that is not publicly known there is no guarantee that a certain installation is secure. Also servers without such vulnerabilities can be successfully attacked through weak passwords.

[edit] WWW scripts

Linux servers may also be used by malware without any attack against the system itself, where e.g. WWW content and scripts are unsufficiently restricted or checked and used by malware to attack visitors. Typically a CGI script (meant for leaving comments) by mistake allows inclusion of code exploiting vulnerabilities in the browser.

[edit] Cross-platform viruses

A new area of concern identified in 2007 is that of cross-platform viruses, driven by the popularity of cross-platform applications. This was brought to the forefront of malware awareness by the distribution of an Openoffice.org virus called Bad Bunny.

Stuart Smith of Symantec wrote the following:

"What makes this virus worth mentioning is that it illustrates how easily scripting platforms, extensibility, plug-ins, ActiveX, etc, can be abused. All too often, this is forgotten in the pursuit to match features with another vendor... [T]he ability for malware to survive in a cross-platform, cross-application environment has particular relevance as more and more malware is pushed out via Web sites. How long until someone uses something like this to drop a JavaScript infector on a Web server, regardless of platform?"^[4]

[edit] Anti-virus applications

There are a number of anti-virus applications available for Linux computers, including:

• Avast! (freeware and commercial versions)
• AVG (freeware and commercial versions)
• Avira (freeware and commercial)
• Bitdefender (freeware and commercial versions)
• ClamAV (free open source software)
• Eset (commercial versions)^[5][6][7]
• F-Secure Linux (commercial)
• Kaspersky Linux Security (commercial)^[8]
• McAfee VirusScan Enterprise for Linux (commercial)^[9]
• Panda Security for Linux (commercial version)^[10]
• Sophos (commercial)
• Symantec AntiVirus for Linux (commercial)^[11]
• Trend Micro ServerProtect for Linux (commercial)

SecurityFocus's Scott Granneman stated,

“

...some Linux machines definitely need anti-virus software. Samba or NFS servers, for instance, may store documents in undocumented, vulnerable Microsoft formats, such as Word and Excel, that contain and propagate viruses. Linux mail servers should run AV software in order to neutralize viruses before they show up in the mailboxes of Outlook and Outlook Express users."[1]

”

Because they are predominately used on mail servers which may send mail to computers running other operating systems, Linux virus scanners generally use definitions for, and scan for, all known viruses for all computer platforms. For example the open source ClamAV "Detects ... viruses, worms and trojans, including Microsoft Office macro viruses, mobile malware, and other threats."^[12]

[edit] Threats

The following is a partial list of known Linux malware. Known malware is not the only or even the most important threat: new malware or attacks directed to specific sites can use vulnerabilities not previously known to the community or not previously used by malware.

[edit] Trojans

• Kaiten - Linux.Backdoor.Kaiten trojan horse^[13]
• Rexob - Linux.Backdoor.Rexob trojan^[14]

[edit] Viruses

• Alaeda - Virus.Linux.Alaeda^[15]
• Bad Bunny - Perl.Badbunny^[4][16]
• Binom - Linux/Binom^[17]
• Bliss
• Brundle^[18]
• Bukowski^[19]
• Diesel - Virus.Linux.Diesel.962^[20]
• Kagob a - Virus.Linux.Kagob.a^[21]
• Kagob b - Virus.Linux.Kagob.b^[22]
• MetaPHOR (also known as Simile)^[23]
• Nuxbee - Virus.Linux.Nuxbee.1403^[24]
• OSF.8759
• Podloso - Linux.Podloso (The iPod virus)^[25][26]
• Rike - Virus.Linux.Rike.1627^[27]
• RST - Virus.Linux.RST.a^[28]
• Satyr - Virus.Linux.Satyr.a^[29]
• Staog
• Vit - Virus.Linux.Vit.4096^[30]
• Winter - Virus.Linux.Winter.341^[31]
• Winux (also known as Lindose and PEElf)^[32]
• Wit virus^[33]
• ZipWorm - Virus.Linux.ZipWorm^[34]

[edit] Worms

• Adm - Net-Worm.Linux.Adm^[35]
• Adore^[36]
• Cheese - Net-Worm.Linux.Cheese^[37]
• Devnull
• Kork^[38]
• Linux/Lion
• Mighty - Net-Worm.Linux.Mighty^[39]
• Millen - Linux.Millen.Worm^[40]
• Ramen worm
• Slapper^[41]
• SSH Bruteforce^[42]

[edit] See also

• List of computer viruses
• List of computer viruses (Numeric)
• List of computer viruses (A-D)
• List of computer viruses (E-K)
• List of computer viruses (L-R)
• List of computer viruses (S-Z)

[edit] References

[edit] External links

• Linux viruses on VirusLibrary
• VX Heavens Virus List

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