Win32/Busky is a family of Trojans that monitor and redirect Internet traffic, gather system information and download unwanted software such as Win32/Renos and Win32/SpySheriff. Win32/Busky may be installed by a Web browser exploit or other vulnerability when visiting a malicious Web site.

What to do now

To detect and remove this threat and other malicious software that may be installed in your computer, run a full-system scan with an up-to-date antivirus product such as the following:
For more information on antivirus software, see

Threat behavior

Win32/Busky is a family of Trojans that monitor and redirect Internet traffic, gather system information and download unwanted software such as Win32/Renos and Win32/SpySheriff. Win32/Busky may be installed by a Web browser exploit or other vulnerability when visiting a malicious Web site. Win32/Busky may also be installed by a Trojan dropper. Trojan droppers for Win32/Busky may be detected as TrojanDropper:Win32/Busky.gen or TrojanDownloader:Win32/Busky.
Win32/Busky consists of one or two dynamic link library Trojan components, depending on the variant. One component functions as a browser helper object, monitoring Web activity and redirecting access to common search sites to another Web site. The other component runs silently and downloads unwanted software programs.
When the Trojan dropper for Win32/Busky executes, it may perform the following actions:
  • Depending on the variant, drops either one or two files into the <system folder> using random file names, such as kpwynle.dll and bgopgyc.dll
  • Modifies the registry to run one of the dropped Trojan components as a Web browser helper object (BHO) that executes whenever Internet Explorer is run, as in this example:
    Adds value: {518BB5B6-C6A6-07E6-658B-01E1AA5CEBE1}\InprocServer32\(default)
    With data: <system folder>\bgopgyc.dll
  • Modifies the registry to run another Trojan component when Windows is started, as in this example:
    Adds value: kpwynle.dll
    With data: <system folder>\rundll32.exe <system folder>\kpwynle.dll,yzviqhc
    To subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  • Creates a "marker" entry in the registry to avoid running Win32/Busky more than once, as in this example:
    Adds value: (default)
    With data: 631930542
    To subkeys:
  • Modifies the registry allowing Win32/Busky to monitor Web browser activity and to redirect certain Internet search queries to certain Web sites:
    Modifies value: MigrateProxy
    With data: 1
    To subkey:
    HKEY_CURRENT_USER\Software\Microsoft\windows\CurrentVersion\Internet Settings\
    Modifies value: ProxyBypass
    With data: 1
    To subkey:
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\
    Modifies value: ProxyEnable
    With data: 0
    To subkey:
    HKLM\SYSTEM\ControlSet001\Hardware Profiles\0001\Software\Microsoft\windows\CurrentVersion\Internet Settings
When Win32/Busky is run, it performs the following actions:
  • Monitors Web site access by Internet Explorer to search sites MSN, Google and Yahoo, and redirects access to an alternate Web site
  • Connects to a remote Web site, using TCP port 80, to download unwanted software such as Win32/Renos and Win32/SpySheriff. These unwanted software programs display erroneous warnings and false notifications of insecurity or infections
  • Connects to a UDP port in the range 3000-3099 and awaits connection attempts from remote attackers
  • Enumerates and sends system information to remote Web sites
Win32/Busky may be affiliated or included with other Trojan installations such as Backdoor:Win32/Cosiam, Trojan:Win32/Tibs, Rootkit:Win32/Rustock and TrojanDownloader:Win32/Vxidl. Win32/Busky may be available on various file sharing networks disguised as a useful program.


The following symptoms may be indicative of a Win32/Busky infection:
  • Presence of a similar registry modification as the following:
    Value: kpwynle.dll
    With data: <system folder>\rundll32.exe <system folder>\kpwynle.dll,yzviqhc
    In subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  • Presence of the following registry subkeys:
  • Google, Yahoo and/or MSN searches are redirected to other sites
  • Pop-up advertisements or windows prompting to download various antispyware or antivirus programs
  • An unexpected connection on UDP port in the port range 3000-3099
  • Possible firewall alerts that a program is attempting to access an IP address in the IP range 88.208.8.x


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
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software, such as Microsoft Security Essentials, that is updated with the latest signature files. For more information, see
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

Alert level: High
This entry was first published on: Jun 20, 2007
This entry was updated on: Apr 17, 2011

This threat is also detected as:
  • Win32/Busky!generic (CA)
  • Trojan-Downloader.Win32.Agent.avm (Kaspersky)
  • Downloader-AXI.gen (McAfee)
  • Trojan:Win32/Busky.gen (Microsoft)
  • W32/Agent.ALFZ (Norman)
  • Troj/Busky-Gen (Sophos)
  • Trojan-Downloader.Win32.Agent.avm (Sunbelt Software)
  • Trojan.Busky (Symantec)
  • TSPY_Agent (Trend Micro)