Worm:Win32/Esfury.X is a worm - a self-propagating program that can spread itself from one computer to another. Worms may spread themselves via a variety of different channels in order to compromise new computers. Commonly, worms may spread directly by copying themselves to removable or network drives, or by attempting to exploit particular vulnerabilities on targeted computers. Worms also often attempt to spread via platforms that require user interaction in order to run. They may send themselves as an attachment to an email or an instant message, or send a link to a copy of themselves in the body of a message. In these cases the message needs to be convincing enough to encourage the victim to click on the link or attachment and run or download a copy of the worm.
creates the following files on an affected computer:
may create the following files on targeted drives when spreading:
- <targeted drive>:\subst .lnk
- <targeted drive>:\125cfaffc54d6d4c49e4\desktop.ini
- <targeted drive>:\125cfaffc54d6d4c49e4\s-1-3-01-4631041401-305419896-464015834-1505\desktop.ini
It also places an autorun.inf file in the root directory of the targeted drive. Such autorun.inf files contain execution instructions for the operating system, so that when the removable drive is accessed from another computer supporting the Autorun feature, the malware is launched automatically.
Note: This worm was observed to write an executable and create an autorun.inf file on a targeted drive in our automated testing environment. This is particularly common malware behavior, generally utilized in order to spread malware from computer to computer.
It should also be noted that autorun.inf files on their own are not necessarily a sign of infection, as they are used by legitimate programs and installation CDs.
Modifies Hosts file
Worm:Win32/Esfury.X modifies the Windows Hosts file. The local Hosts file overrides the DNS resolution of a website URL to a particular IP address. Malicious software may make modifications to the Hosts file in order to redirect specified URLs to different IP addresses. Malware often modifies an affected computer's Hosts file in order to stop users from accessing websites associated with particular security-related applications (such as antivirus for example).
The malware terminates the following processes should they be running on an affected computer:
Contacts remote hosts
The malware may contact the following remote hosts using port 80:
Commonly, malware may contact a remote host for the following purposes:
- To confirm Internet connectivity
- To report a new infection to its author
- To receive configuration or other data
- To download and execute arbitrary files (including updates or additional malware)
- To receive instruction from a remote attacker
- To upload data taken from the affected computer
This malware description was produced and published using our automated analysis system's examination of file SHA1 08d805c727ac4fd895a26d3b6f7aab98ebbad0aa.