BKDR_HORSMY.A
Backdoor.Hormesu (Symantec); TrojanSpy:Win32/Fucobha.A (Microsoft); Trojan-Downloader.Win32.Agent.swbo (Kaspersky)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This backdoor is capable of sending system information to a remote server. If a connection to the server is established, it may download, upload or execute arbitrary files into the system.
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It does not have any propagation routine.
TECHNICAL DETAILS
77,824 bytes
DLL
Yes
11 Nov 2011
Compromises system security, Connects to URLs/IPs
Arrival Details
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This backdoor adds the following mutexes to ensure that only one of its copies runs at any one time:
- myhorsemutex
It injects itself into the following processes as part of its memory residency routine:
- EXPLORER.EXE
Propagation
This backdoor does not have any propagation routine.
NOTES:
Backdoor Routine
It connects to the following server via HTTP POST / GET:
- www. {BLOCKED} bit.com
Initially, it sends the information contained in %System%\tmp.dat via HTTP POST, then awaits for commands from the remote computer. Once connection is established, it can do the following:
- Upload Files
- Download Files
- Execute file
Currently, the server is inaccessible.
Rootkit Capabilities
It does not have rootkit capabilities.
Other Details
It creates the following file that is also deleted after use:
- %System%\tmp.dat
(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)
The said file is non-malicious and contains the following information:
- Host Name
- IP address
- List of processes
- OS language version
- OS version
- Path of System directory
This backdoor can use the following user agent when communicating with the server:
- mydownload
- MyAgent
It does not exploit any vulnerability.
SOLUTION
9.200
8.582.01
18 Nov 2011
8.583.00
19 Nov 2011
Step 1
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Step 2
Scan your computer with your Trend Micro product and note files detected as BKDR_HORSMY.A
Step 3
Restart in Safe Mode
Step 4
Search and delete this file
- %System%\tmp.dat
Step 5
Search and delete the file detected as BKDR_HORSMY.A
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_HORSMY.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
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