Zlob or the Zlob Trojan is a trojan that can infect users' computers by pretending to be a fake video codec in the form of Active X but can also infect the host's computer by rogue software. It was first detected in late 2005 but only started gaining attention in mid-2006.<ref name="tm">"The ZLOB Show: Trojan Poses as Fake Video Codec, Loads More Threats". Trend Micro. http://www.trendmicro.com/vinfo/secadvisories/default6.asp?VNAME=The+ZLOB+Show%3A+Trojan+poses+as+fake+video+codec%2C+loads+more+threats. Retrieved on 2007-11-26. </ref> Once installed, it displays popup ads with an appearance similar to real Microsoft Windows warning popups, informing the user that their computer is infected with spyware. Clicking these popups triggers the download of a fake anti-spyware program (such as Virus Heat and MS Antivirus in which the trojan is hidden.<ref name="tm" />
According to F-Secure, a computer security firm, they have discovered 32 variants of this trojan. Other variants continue to be discovered on a daily basis and are added to the detection signatures of various commercial anti-virus products.<ref name="MacTrojan">Tung, Liam (2007-11-08). "Multiplying Mac Trojan not epidemic yet". CNET News. http://www.news.com/Multiplying-Mac-Trojan-not-epidemic-yet/2100-7349_3-6217540.html. Retrieved on 2007-11-26. </ref> Some variants of the Zlob family, like the so-called DNSChanger, adds rogue DNS name servers to the Registry of Windows-based computers,<ref>Podrezov, Alexey (2005-11-07). "F-Secure Virus Descriptions: DNSChanger". F-Secure Corporation. http://www.f-secure.com/v-descs/dnschang.shtml. Retrieved on 2007-11-26. </ref> network settings of Macintosh computers<ref>SANS Internet Storm Center; Cooperative Network Security Community - Internet Security - isc</ref> and attempts to hack into any detected router to change the DNS settings and therefore could potentially re-route traffic from legitimate web sites to other suspicious web sites.
The trojan has also been linked to downloading atnvrsinstall.exe which uses the Windows Security shield icon to look as if it is an Anti Virus installation file from Microsoft. Having this file initiated can wreak havoc on computers and networks. One symptom is random computer shutdowns or reboots with random comments. This is caused by the programs using Scheduled Tasks to run a file called "zlberfker.exe".
PHSDL - Project Honeypot Spam Domains List<ref>PHSDL - Project Honeypot Spam Domains List</ref> tracks and catalogues Zlob spam Domains. Some of the domains on the list are redirects to porn sites and various video watching sites that show a number of inline videos. Clicking on the video to play activates a request to download an ActiveX codec which is malware. It prevents the user from closing the browser in the usual manner. Other variants of Zlob Trojan installation are in the form of computer scan that comes as a Java cab.<ref>PHSDL Zlob Trojan Forum Spam Hijacking Attempt Documentation</ref>
Some evidence confirms that the creator of this trojan is most likely the Russian Business Network which is famous for the originator of MPack and its hosting of illegal and dubious businesses.
- Zlob trojan description and removal instructions
- List of ActiveX Zlob Trojan fake codecs and other misleading Zlob-installers
- Listing of 113 fake codec domains
- Flash's Security Blog, a blog listing fake codecs and rogue security software.
- S!Ri.URZ, SmitfraudFix.
- Zlob/VideoAccess/Trojan.Win32.DNSChanger - malekal.com (fr)
Anti Zlob Malware Forums