Trojan:Agent/BKBB is a multipurpose trojan that infects Windows systems to establish remote access, steal credentials, and deploy additional payloads. First cataloged by several antivirus vendors in the early 2010s, this threat belongs to the broad Agent trojan family—a loose collection of malware variants characterized by modularity and rapid mutation to evade signature-based detection. Once installed, it runs silently in the background, communicating with command-and-control servers to receive instructions while harvesting sensitive data from the compromised machine.
This trojan typically arrives bundled with pirated software, fake codec installers, or malicious email attachments disguised as invoices or shipping notifications. Its primary goal is to open a backdoor for attackers while remaining undetected for as long as possible. Users often don't realize they're infected until they notice unexplained network activity, degraded system performance, or unauthorized account access attempts.
Threat Profile
| Attribute | Details |
|---|---|
| Malware Family | Trojan:Agent (generic backdoor/infostealer family) |
| Known Aliases | Agent.BKBB, Trojan.Agent.BKBB, Win32/Agent.BKBB, TROJ_AGENT.BKBB |
| Platform | Windows XP, Vista, 7, 8, 8.1, 10, 11 (32-bit and 64-bit) |
| First Documented | Approximately 2011–2012 (variants continue to appear) |
| Primary Distribution | Software bundles, malicious email attachments, drive-by downloads, exploit kits |
| Persistence Mechanism | Registry Run keys, scheduled tasks, Windows services (varies by variant) |
| Core Capabilities | Remote command execution, keylogging, credential theft, screenshot capture, file download/upload, process injection |
| Network Behavior | Connects to hard-coded or domain-generation-algorithm (DGA) C2 servers over HTTP/HTTPS, often on non-standard ports |
| Common IoCs | Random executables in %APPDATA% or %LOCALAPPDATA%, suspicious outbound connections to unfamiliar IPs, new scheduled tasks with random names |
| Stealth Techniques | Rootkit-like hiding (some variants), process injection into legitimate system processes, encrypted C2 traffic |
| Data Exfiltration | Credentials from browsers/email clients, cryptocurrency wallets, FTP clients, system information, files from desktop/documents |
| Removal Difficulty | Moderate to high—manual removal requires registry editing and safe mode; professional tools recommended |
How It Spreads
Trojan:Agent/BKBB relies on social engineering and software supply-chain abuse to reach your computer. The most common infection vector is bundled freeware: users download what appears to be a legitimate utility—often video converters, system optimizers, or PDF readers—from unofficial download sites. The installer quietly drops the trojan alongside the advertised program, and many users click through the prompts without noticing the extra payload.
Email attachments represent another major distribution channel. Attackers send messages impersonating shipping companies (FedEx, UPS, DHL), financial institutions, or business partners. The attachment might be a ZIP archive containing an executable disguised with a double extension (like invoice.pdf.exe) or a document with malicious macros. When the user opens the attachment, the trojan installs silently while displaying a decoy document or error message to avoid suspicion.
Drive-by downloads from compromised or malicious websites also spread this threat. Outdated browser plugins—especially Flash Player, Java, and Silverlight—provide exploitable entry points. When you visit an infected site, the exploit kit probes for vulnerable software and delivers the trojan without any visible warning. Some variants also propagate through removable media like USB drives, using autorun features to spread to new systems.
- Software bundles: Pirated programs, fake codec packs, and freeware from untrusted download portals
- Malicious email attachments: Fake invoices, shipping notifications, tax documents, and resume submissions
- Exploit kits: Automated attack frameworks on compromised websites targeting outdated browser plugins
- Fake updates: Pop-ups claiming your Flash Player, Java, or video codec needs updating
- Peer-to-peer networks: Infected files shared on torrent sites, often embedded in cracked software or key generators
- Malvertising: Malicious advertisements on legitimate websites that redirect to exploit landing pages
- USB/removable media: Infected drives that use autorun to execute the trojan when connected
What It Does On Your Machine
Once Trojan:Agent/BKBB executes, it copies itself to a hidden location in your user profile folder—typically within %APPDATA% or %LOCALAPPDATA% under a randomly generated subfolder name (a long GUID-style string like {8F4D2E3A-C1B7-49A2-8E6F-D3C9B2A14E7C}). The executable itself often has a random name composed of alphanumeric characters to avoid pattern-matching detection. This makes it difficult to spot in a file listing unless you know what you're looking for.
To survive reboots, the trojan creates persistence mechanisms in the Windows registry. The most common approach is adding a Run key under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run or the equivalent LocalMachine hive for system-wide persistence. Some variants also install themselves as Windows services or create scheduled tasks that trigger at logon or at regular intervals. These tasks often have innocuous-sounding names like "SystemUpdateCheck" or "WindowsDefenderUpdate" to blend in with legitimate system processes.
The trojan's primary mission is data theft and remote control. It typically installs a keylogger component that captures everything you type—passwords, credit card numbers, private messages—and stores them in an encrypted log file for later exfiltration. Browser credential theft is another core capability: the malware scans browser profile folders for saved passwords, cookies, and autofill data from Chrome, Firefox, Edge, and Internet Explorer. Some variants also target email clients like Outlook and Thunderbird, extracting account credentials and contact lists.
Simultaneously, Trojan:Agent/BKBB establishes contact with its command-and-control server. It sends an initial beacon containing basic system information: your computer name, Windows version, installed antivirus software, IP address, and a unique infection ID. The C2 server can then issue commands to download additional malware, execute arbitrary files, capture screenshots, upload sensitive documents, or even record audio through your microphone if one is present. The communication often occurs over encrypted HTTPS connections to evade network monitoring, and some variants use domain generation algorithms to find backup C2 servers if the primary one is taken offline.
Manual Removal — Step by Step
Disconnect From the Internet
Immediately unplug your Ethernet cable or disable your Wi-Fi adapter. This prevents the trojan from receiving new commands, exfiltrating more data, or downloading additional payloads. Leave the computer disconnected throughout the removal process except when you need to download security tools on a clean device.
Boot Into Safe Mode With Networking
Restart your computer and press F8 (or Shift+F8 on newer systems) repeatedly during boot to access the Advanced Boot Options menu. Select "Safe Mode with Networking." This loads only essential drivers and prevents most malware from executing automatically. On Windows 10/11, you can also hold Shift while clicking Restart, then navigate to Troubleshoot → Advanced Options → Startup Settings → Restart → press 5 for Safe Mode with Networking.
Show Hidden Files and Folders
Open File Explorer, click the View tab, and check "Hidden items." Then go to Options → Change folder and search options → View tab → select "Show hidden files, folders, and drives" and uncheck "Hide protected operating system files." Click OK. This makes the trojan's files visible so you can locate and delete them.
Identify and Terminate Malicious Processes
Press Ctrl+Shift+Esc to open Task Manager. Look for unfamiliar processes, especially those with random names or high memory usage. Right-click suspicious entries and select "Open file location" to see where they're running from. If the path is inside %LOCALAPPDATA% or %APPDATA% with GUID-like folder names, note the path and then end the process. Be careful not to terminate legitimate Windows processes—when in doubt, search the process name online before ending it.
Remove Registry Persistence Entries
Press Win+R, type regedit, and press Enter. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run. Look for entries pointing to executables in %LOCALAPPDATA% or %APPDATA% with suspicious folder names (GUIDs, random character strings). Right-click these entries and delete them. Also check HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce and the LocalMachine equivalent.
Delete Scheduled Tasks
Press Win+R, type taskschd.msc, and press Enter to open Task Scheduler. Expand Task Scheduler Library and look for tasks with generic names like "SystemUpdateCheck" or "WindowsDefenderUpdate" that you didn't create. Click each suspicious task, check the Actions tab to see what it executes, and if it points to the malware path, right-click and delete it. Pay attention to tasks set to run at logon or at startup.
Delete the Malware Files and Folders
Using File Explorer, navigate to the paths you identified earlier (typically C:\Users\[YourName]\AppData\Local\{GUID}\ or C:\Users\[YourName]\AppData\Roaming\{GUID}\). Delete the entire folder. If Windows says the file is in use, restart in Safe Mode again and try deleting before any processes load. Also check your Temp folders (%TEMP% and C:\Windows\Temp) for related files.
Run a Full Scan With Malwarebytes
Download Malwarebytes Free on a clean computer (or reconnect to the internet briefly in Safe Mode if you must) and install it. Update the definitions, then run a full "Threat Scan." This will catch any remnants or additional malware the trojan may have downloaded. Quarantine and remove all detected threats. Follow up with a scan using Windows Defender or your preferred antivirus software as a second opinion.
Reset Your Browsers and Clear Data
If the trojan accessed your browser credentials, reset each browser to defaults. In Chrome, go to Settings → Reset and clean up → Restore settings to their original defaults. In Firefox, type about:support in the address bar and click "Refresh Firefox." In Edge, go to Settings → Reset settings → Restore settings to their default values. This removes malicious extensions and clears stored credentials that may have been compromised.
Change All Important Passwords
Because this trojan steals credentials, assume any password you typed while infected was captured. From a different, clean device, change passwords for your email, banking, social media, work accounts, and any other sensitive services. Enable two-factor authentication wherever possible. Do not change passwords on the infected computer until you're certain the malware is completely removed and the system has been scanned clean.
Reboot Normally and Verify Removal
Restart your computer in normal mode and reconnect to the internet. Monitor Task Manager for unusual processes and check your startup programs (Task Manager → Startup tab) to ensure nothing suspicious reappears. Run another quick scan with Malwarebytes and Windows Defender to confirm the system is clean. If any symptoms persist—unexpected network activity, new unknown processes, browser redirects—the infection may not be fully removed, and professional assistance is recommended.
Prevention
- Download software only from official sources. Avoid third-party download sites that bundle extra software. Get programs directly from the developer's website or use the Microsoft Store for Windows applications.
- Keep Windows and all software updated. Enable automatic updates for Windows, and regularly update browsers, PDF readers, office suites, and plugins. Most exploits target known vulnerabilities that have already been patched.
- Use reputable antivirus software and keep it current. Windows Defender provides good baseline protection, but consider adding a second-opinion scanner like Malwarebytes for periodic checks. Ensure real-time protection is enabled.
- Be skeptical of email attachments and links. Never open attachments from unknown senders. Even if an email looks like it's from a known company, verify the sender's address carefully. When in doubt, contact the company directly through official channels rather than clicking links in the email.
- Disable macros in Office documents by default. Go to File → Options → Trust Center → Trust Center Settings → Macro Settings and select "Disable all macros with notification." Only enable macros for documents from trusted sources that you were expecting to receive.
- Remove or disable unnecessary browser plugins. Uninstall Flash Player (it's obsolete), Java applets, and other plugins you don't actively use. These are common exploit targets.
- Use a standard user account for daily tasks. Create a separate administrator account for installing software and making system changes. Run your daily work from a standard user account, which limits malware's ability to make system-wide changes.
- Back up your data regularly to an external drive or cloud service. If you do get infected, having clean backups means you can restore your files without paying ransoms or risking data loss. Disconnect backup drives when not in use so malware can't encrypt them.
Bring It In
If you're dealing with Trojan:Agent/BKBB or suspect your computer is infected but don't want to risk doing the removal yourself, bring it to Computer Repair Roswell. We've been cleaning infected computers for Roswell residents and businesses since 2006, and we've seen every variation of trojan malware imaginable. Our technicians use professional-grade tools and manual inspection techniques to ensure complete removal—not just quarantining the obvious files but hunting down persistence mechanisms, rootkit components, and any secondary infections the trojan may have downloaded.
We're located at 1925 Vaughn Road in Roswell, just a few minutes from Highway 400 and Holcomb Bridge Road. Call us at (770) 594-5923 to describe your symptoms and schedule a time to drop off your computer, or just stop by—we offer same-day diagnostics for most infections. We'll give you a clear assessment of the damage, a fair price quote before we begin work, and a realistic timeline for when you'll have your clean machine back. Most trojan removals are completed within 24 hours, and we always follow up with security recommendations to help you avoid reinfection. Don't let malware hold your data hostage or steal your credentials—let's get your computer back to safe, reliable operation.