Win32/Afcore is a trojan that connects to a remote server to retrieve commands that are executed on the affected computer.
Installation
Win32/Afcore is installed by a dropper and is present as a DLL. When run, it drops the payload component, modifies the registry and restarts the Windows Explorer process. When run, the Win32/Afcore dropper creates the following Win32/Afcore trojan files:
The dropper also creates additional data files as the following:
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<system folder>\<random file name 1>.dat (for example "cabviuw.dat")
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<system folder>\<random file name 2>.dat (for example "compobpq.dat")
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<system folder>\<random file name 3>.dat (for example "kbdkaob.dat")
The trojan file copy created in the %TEMP% folder is executed. The registry is modified to run the Windows system folder copy of the DLL at each Windows start.
In subkey: HKLM\Software\Classes\CLSID\{ random UUID }
Sets value: "(default)"
With data: "<random name without extension>"
In subkey: HKLM\SOFTWARE\Classes\CLSID\{ random UUID }\InprocServer32
Sets value: "(default)"
With data: "<system folder>\<random file name>.dll"
To subkey: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\<random name without extension>
Adds value: "(default)"
With data: "{ random UUID }"
After installing Win32/Afcore, the dropper deletes itself by executing instructions within a command shell (cmd.exe).
Payload
Terminates Windows Explorer
Win32/Afcore terminates the Windows Explorer process so that restarting the Windows Explorer process will load the installed trojan.
Captures credentials
Win32/Afcore uses code from a freeware utility to export certificates marked as non-exportable from the Windows certificate store. The trojan also monitors network traffic for certain transactions such as mobile payments and site login events. Captured credentials could then be sent to a remote host.
Allows remote access and control
Win32/Afcore allows limited access and control from a remote attacker. It could perform the following actions:
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modify the registry to run at Windows start
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restart or shutdown its currently running process
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monitor window sockets
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make connections to a remote host to transmit data
Analysis by Jaime Wong
Take the following steps to help prevent infection on your computer:
- Enable a firewall on your computer.
- Get the latest computer updates for all your installed software.
- Use up-to-date antivirus software.
- Limit user privileges on the computer.
- Use caution when opening attachments and accepting file transfers.
- Use caution when clicking on links to webpages.
- Avoid downloading pirated software.
- Protect yourself against social engineering attacks.
- Use strong passwords.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor websites.
You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
Use up-to-date antivirus software
Limit user privileges on the computer
Starting with Windows Vista and Windows 7, Microsoft introduced User Account Control (UAC), which, when enabled, allowed users to run with least user privileges. This scenario limits the possibility of attacks by malware and other threats that require administrative privileges to run.
You can configure UAC in your computer to meet your preferences:
Use caution when opening attachments and accepting file transfers
Exercise caution with email and attachments received from unknown sources, or received unexpectedly from known sources. Use extreme caution when accepting file transfers from known or unknown sources.
Use caution when clicking on links to webpages
Exercise caution with links to webpages that you receive from unknown sources, especially if the links are to a webpage that you are not familiar with, unsure of the destination of, or suspicious of. Malicious software may be installed in your computer simply by visiting a webpage with harmful content.
Avoid downloading pirated software
Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information, see '
The risks of obtaining and using pirated software'.
Protect yourself from social engineering attacks
While attackers may attempt to exploit vulnerabilities in hardware or software to compromise a computer, they also attempt to exploit vulnerabilities in human behavior to do the same. When an attacker attempts to take advantage of human behavior to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted computer. For more information, see '
What is social engineering?'.
Use strong passwords
Attackers may try to gain access to your Windows account by guessing your password. It is therefore important that you use a strong password – one that cannot be easily guessed by an attacker. A strong password is one that has at least eight characters, and combines letters, numbers, and symbols. For more information, see
http://www.microsoft.com/protect/yourself/password/create.mspx.
