Trojan.Win32.Sasfis_82570ebceb

Dynamic Analysis

Payload

Behaviour	Description
WormAutorun	A worm can spread via removable drives. It writes its executable and creates "autorun.inf" scripts on all removable drives. The autorun script will execute the Trojan's file once a user opens a drive's folder in Windows Explorer.
IRCBot	A bot can communicate with command and control servers via IRC channel.

Process activity

The Trojan creates the following process(es):

winlog.exe:1712
82570ebcebe0aaa2ceb791fe6a7f565c.exe:1116

The Trojan injects its code into the following process(es):

winlog.exe:1680

File activity

The process winlog.exe:1680 makes changes in a file system.

The Trojan deletes the following file(s):

%Documents and Settings%\%current user%\Application Data\Microsoft\winlog.exe (0 bytes)

The process 82570ebcebe0aaa2ceb791fe6a7f565c.exe:1116 makes changes in a file system.

The Trojan creates and/or writes to the following file(s):

%Documents and Settings%\%current user%\Application Data\Microsoft\winlog.exe (2105 bytes)

Registry activity

The process winlog.exe:1680 makes changes in a system registry.

The Trojan creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "4F 70 2F E1 AC 4F 1A 8E 66 EE A1 5E 13 00 2A 33"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"AppData" = "%Documents and Settings%\%current user%\Application Data"

To automatically run itself each time Windows is booted, the Trojan adds the following link to its file to the system registry autorun key:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
"winlog.exe" = "%Documents and Settings%\%current user%\Application Data\Microsoft\winlog.exe"

The process 82570ebcebe0aaa2ceb791fe6a7f565c.exe:1116 makes changes in a system registry.

The Trojan creates and/or sets the following values in system registry:

[HKLM\SOFTWARE\Microsoft\Cryptography\RNG]
"Seed" = "D1 01 A8 5A D7 F3 C6 F0 CD D5 C0 8B 1D 73 E4 CB"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd73-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Cookies" = "%Documents and Settings%\%current user%\Cookies"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Cache" = "%Documents and Settings%\%current user%\Local Settings\Temporary Internet Files"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Common Documents" = "%Documents and Settings%\All Users\Documents"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Desktop" = "%Documents and Settings%\%current user%\Desktop"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd72-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{b98117e8-75ca-11e2-81b2-000c293708fb}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"AppData" = "%Documents and Settings%\%current user%\Application Data"

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Common Desktop" = "%Documents and Settings%\All Users\Desktop"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\{c155cd75-744b-11e2-8294-806d6172696f}]
"BaseClass" = "Drive"

[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders]
"Personal" = "%Documents and Settings%\%current user%\My Documents"

[HKCU\Software\Microsoft\Windows\ShellNoRoam\MUICache\%Documents and Settings%\%current user%\Application Data\Microsoft]
"winlog.exe" = "winlog"

The Trojan modifies IE settings for security zones to map all urls to the Intranet Zone:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap]
"IntranetName" = "1"

The Trojan modifies IE settings for security zones to map all local web-nodes with no dots which do not refer to any zone to the Intranet Zone:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap]
"UNCAsIntranet" = "1"

The Trojan modifies IE settings for security zones to map all web-nodes that bypassing proxy to the Intranet Zone:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap]
"ProxyBypass" = "1"

Network activity (URLs)

No activity has been detected.

Rootkit activity

No anomalies have been detected.

Propagation

A worm can spread via removable drives. It writes its executable and creates "autorun.inf" scripts on all removable drives. The autorun script will execute the Trojan's file once a user opens a drive's folder in Windows Explorer.

Removals

Remove it with Ad-Aware

1. Click (here) to download and install Ad-Aware Free Antivirus.
2. Update the definition files.
3. Run a full scan of your computer.

Manual removal*

1. Terminate malicious process(es) (How to End a Process With the Task Manager):

   winlog.exe:1712
   82570ebcebe0aaa2ceb791fe6a7f565c.exe:1116
   

2. Delete the original Trojan file.
   
3. Delete or disinfect the following files created/modified by the Trojan:

   %Documents and Settings%\%current user%\Application Data\Microsoft\winlog.exe (2105 bytes)

4. Delete the following value(s) in the autorun key (How to Work with System Registry):

   [HKCU\Software\Microsoft\Windows\CurrentVersion\Run]
   "winlog.exe" = "%Documents and Settings%\%current user%\Application Data\Microsoft\winlog.exe"

5. Find and delete all copies of the worm's file together with "autorun.inf" scripts on removable drives.
   
6. Reboot the computer.
   

*Manual removal may cause unexpected system behaviour and should be performed at your own risk.

Static Analysis

Network Activity

Map

Strings from Dumps