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What kind of malware is Horabot?
Horabot is part of the campaign where threat actors infect machines with a banking Trojan and spam tool. This campaign primarily focuses on Spanish-speaking users in the Americas. Horabot enables attackers to manipulate Outlook mailboxes, extract email addresses, distribute phishing emails with harmful attachments, and acquire login credentials and security codes.
More about Horabot
The malicious payloads used in this campaign are specifically crafted to steal sensitive information, avoid detection, and propagate further phishing emails to the contacts of the victims. The banking Trojan focuses on extracting critical data, including login credentials and security codes for financial transactions, while also logging keystrokes and manipulating the clipboard data of the victim's machine.
Horabot is a PowerShell-based botnet program specifically designed for Outlook phishing. It incorporates Visual Basic code that empowers threat actors to manipulate the victim's Outlook mailbox, extract email addresses from contacts, and distribute phishing emails with malicious HTML attachments to all recipients within the victim's mailbox.
The attackers aim to distribute the banking Trojan to obtain the victim's credentials and financial information. In addition, they deploy Horabot and a separate spam tool to further propagate the infection by sending phishing emails to all verified email addresses within the victim's mailbox. Cybercriminals employ this strategy to minimize the risk of their phishing infrastructure being traced.
| Name | Horabot spam tool |
| Threat Type | Trojan, malicious spam tool |
| Detection Names | Avast (Win32:Trojan-gen), Combo Cleaner (Trojan.GenericKD.67338119), ESET-NOD32 (Multiple Detections), Kaspersky (Trojan-Banker.Win32.Ponteiro.acu), Microsoft (Trojan:Win32/Casdet!rfn), Full List (VirusTotal) |
| Symptoms | Malicious programs like Horabot are often designed to stealthily infiltrate the victim's computer and remain silent, and thus no particular symptoms are clearly visible on an infected machine. |
| Distribution methods | Infected email attachments, social engineering. |
| Damage | Stolen sensitive information, identity theft, financial loss, and more. |
| Malware Removal (Windows) |
To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. Download Combo CleanerTo use full-featured product, you have to purchase a license for Combo Cleaner. 7 days free trial available. Combo Cleaner is owned and operated by RCS LT, the parent company of PCRisk.com. |
Possible damage
Harabot can cause significant damage by compromising victims' Outlook mailboxes, extracting email addresses, and sending phishing emails with malicious attachments. This can result in the theft of sensitive information, such as login credentials and financial data, leading to potential financial loss, identity theft, unauthorized access to personal accounts, and other issues.
How did Horabot infiltrate my computer?
The infection process starts with a phishing email disguised as a tax-related message containing an HTML attachment posing as a payment receipt. Upon opening the HTML file, a series of URL redirections occur, ultimately leading the victim to an HTML page hosted on an AWS instance controlled by the attacker.
Upon clicking the hyperlink on the page, the victim downloads a RAR archive that includes a CMD batch file. Executing this file triggers the download of a PowerShell script from the C2 server, which retrieves trojan DLLs and a collection of genuine executables. These trojans are then executed to fetch the final payloads from another C2 server. These payloads consist of a PowerShell downloader script and the Horabot binary.
How to avoid installation of malware?
Be cautious while clicking on suspicious links or downloading files from untrusted sources (e.g., P2P networks, third-party downloaders, free file hosting pages, etc.). Download software from official pages. Regularly update your operating system, software, and antivirus programs to ensure you have the latest security patches.
Additionally, exercise caution when opening email attachments, especially from unknown or suspicious senders. If you believe that your computer is already infected, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.
How to remove malware manually?
Most trojan infections can be removed by running a full system scan with Combo Cleaner. The full manual procedure below is for cases where automatic removal failed, where you want to verify a scan caught everything, or where the threat has multiple persistence points.
Disconnect from the network
Unplug your Ethernet cable and turn off Wi-Fi. If you're on a laptop, the airplane-mode key works fastest.
Many trojans exfiltrate data - saved browser passwords, banking sessions, screenshots - and accept remote commands. Cutting the network stops both immediately. Keep it disconnected until Phase 4.
Boot into Safe Mode with Networking
Safe Mode loads a minimal set of drivers and stops most malware from auto-running. "With Networking" lets you download tools - re-enable Wi-Fi only after you've booted in.
Open . Click Restart now next to Advanced startup.
Your computer will restart into the "Choose an option" menu. Click . After the second reboot, press 5 or F5.
Click the Windows logo, hold Shift, click the Power icon and choose Restart. In the Choose an option screen, click . Press F5.
Windows 8
Go to the Start Screen, type Advanced, select Settings → Advanced startup options → Restart now → Troubleshoot → Advanced options → Startup settings → Restart → F5.
Note: Windows 8 reached end-of-life in January 2023 - running on it puts you at much higher risk of reinfection.
Windows 7
Click Start → Shut Down → Restart → OK. As the system boots, press F8 repeatedly until the Windows Advanced Options menu appears, then choose Safe Mode with Networking.
Note: Windows 7 reached end-of-life in January 2020 - running on it puts you at much higher risk of reinfection.
Inspect running processes with Process Explorer
Download Process Explorer from Microsoft Sysinternals. Run it as Administrator. Click and .
Sort by "Verified Signer." Anything unsigned running from %AppData%, %LocalAppData%, %Temp%, or %ProgramData% is suspicious. Right-click → Properties to see the full image path. Right-click → "Search Online" to look up unfamiliar process names.
Task Manager hides full file paths, doesn't show digital signatures, and groups processes in ways that make malware easy to miss. Process Explorer is the same tool Microsoft engineers use.
Map every persistence point with Autoruns
Download Autoruns. Right-click Autoruns.exe and choose Run as administrator - without elevation, Autoruns can't inspect protected registry hives.
In the menu, open and , then click Refresh.
Modern trojans don't just live in startup. Walk through these tabs and look for unsigned or unfamiliar entries:
- Logon - classic Run/RunOnce keys
- Scheduled Tasks - frequent hiding spot, especially tasks with PowerShell, MSHTA, or rundll32 actions
- Services - unsigned services in non-Microsoft folders
- WMI - Event Subscriptions are a stealthy persistence mechanism (MITRE T1546.003)
- Image Hijacks - Image File Execution Options "Debugger" abuse
- AppInit - DLLs loaded into every GUI process
- Browser plug-ins - unsigned add-ons across all installed browsers
Right-click any suspicious entry → "Jump to Image" to see the actual file. Right-click → "Search Online" opens VirusTotal for the file hash. Don't delete yet - just write down the file paths and entry names. We'll remove them after the scans.
Check the hosts file and DNS settings
Trojans often redirect bank, antivirus, and update domains to attacker-controlled servers by editing the hosts file or DNS settings.
Hosts file: Open Notepad as Administrator and open C:\Windows\System32\drivers\etc\hosts. Legitimate entries are commented with #. Any uncommented IP-to-domain mapping is suspicious - especially redirects for microsoft.com, windowsupdate, or your bank.
DNS settings: Open Command Prompt as Administrator and run ipconfig /all. Confirm your DNS servers point to your ISP, your router, or a known public resolver (Cloudflare 1.1.1.1, Google 8.8.8.8). Then open and verify both DNS and DNS over HTTPS (DoH) settings haven't been hijacked.
A clean PC with hijacked DNS is still a compromised PC. You'll think you're at chase.com and you'll be at the attacker's clone.
No single antivirus catches everything. The order below is intentional: offline scan first (catches rootkits before Windows fully loads), then on-demand scanners on the running system, then manual cleanup of anything they missed.
Run Microsoft Defender Offline
Reboot to normal Windows. Open . Select Microsoft Defender Antivirus (offline scan) and click Scan now. Your computer will restart into a stripped-down environment and scan before the full operating system loads.
Rootkits and bootkits hide from any scanner running on the same Windows session that's already infected. A pre-boot offline scan sees the disk before the malware can hide itself.
VB100 certified. Includes anti-trojan, registry/persistence scanning, anti-spyware in one pass. The 7-day free trial is available.
Download Combo CleanerRun Combo Cleaner full system scan
Install Combo Cleaner and run a full system scan (not the quick scan). Let it complete fully, review the detected threats, and apply the recommended actions. Combo Cleaner will quarantine known trojans and registry persistence.
Run Microsoft Safety Scanner as a second-opinion scan
Download Microsoft Safety Scanner (MSERT.exe), Microsoft's free on-demand tool. The binary expires every 10 days, which means every download has the latest signatures. Run a full scan after Combo Cleaner to catch anything one engine alone might miss.
Different scanning engines catch different threats. Running an additional Microsoft scan after Combo Cleaner is the single most underused verification step in malware removal.
Manually remove anything still listed in Autoruns
Reopen Autoruns. Anything you flagged in Step 4 that's still present hasn't been caught by the automated scans. For each remaining suspicious entry: right-click → Delete in Autoruns (this removes the persistence registration), then navigate to the file path and delete the actual file. Empty the Recycle Bin.
Some malware files reappear after deletion because something else on the system recreates them. If you delete a file and it returns within minutes, you have a remaining persistence point that Autoruns didn't show - usually a service or scheduled task running under SYSTEM. Re-run the scans from Steps 6-8 or proceed to a clean install (see end of guide).
Reset browsers and clear notification permissions
Trojans and adware frequently hijack browsers - change the default search engine, install rogue extensions, or grant themselves notification permissions to keep displaying scam pop-ups even after the malware is gone.
- Chrome: visit
chrome://settings/resetand click "Restore settings to their original defaults." Then visitchrome://settings/content/notificationsand remove any unfamiliar sites. - Edge: visit
edge://settings/reset. Then checkedge://settings/content/notifications. - Firefox: open
about:supportand click Refresh Firefox (Firefox uses "Refresh," not "Reset"). Then check Settings → Privacy & Security → Permissions → Notifications.
Review installed extensions in each browser and remove anything you don't recognize, especially extensions you didn't install yourself.
Re-enable Defender, Tamper Protection, and update everything
Many trojans disable security software. Open and confirm Real-time protection, Cloud-delivered protection, and Tamper Protection are all turned on. Tamper Protection prevents malware from disabling Defender silently.
Then run Windows Update () and update your browsers and applications. The infection vector that let the trojan in originally usually involves outdated software.
Change passwords from a clean device
If the trojan was an info-stealer (Lumma, RedLine, Vidar, and similar are extremely common), assume every password saved in your browser is compromised. Change them from a different, known-clean device - your phone is fine if it's not infected.
Recommended order:
- Primary email first - it's the recovery hub for everything else
- Banking and financial accounts
- Password manager master password (if you use one)
- Social media, shopping, and remaining accounts
Where available, enable phishing-resistant multi-factor authentication (passkeys / FIDO2 hardware keys / authenticator apps) - SMS-based MFA is bypassable by sophisticated attackers.
Verify the clean and monitor for 7 days
Reconnect to the network and run one final full scan with Combo Cleaner. Open Task Manager (Ctrl + Shift + Esc) and switch to the Startup apps tab - confirm nothing suspicious has reappeared.
Over the next 7 days, watch for symptom recurrence: unexpected high CPU usage, unknown processes returning, browser redirects, or pop-ups. If anything returns, you missed a persistence point and the procedure needs to be repeated - or you may have a deeper compromise that requires a clean install.
When to clean install Windows instead
Manual removal isn't always the right answer. Reinstalling Windows from scratch is the only way to be 100% certain when:
- The malware reappears after every removal attempt
- A bootkit or UEFI rootkit was detected (this class of threat sits below the operating system and survives a normal Windows reinstall)
- A confirmed credential-theft trojan ran with administrator privileges (Lumma, RedLine, Vidar) - the system likely has multiple unknown payloads
- The PC is used for online banking, business email, or anything where partial doubt isn't acceptable
A clean install is a 30-60 minute process: Windows 11 reinstall via . Back up documents to external storage first, scan the backup with Combo Cleaner before restoring it, and reinstall applications fresh - never restore them from a backup of the infected system.
Important: Manual removal requires advanced computer skills. If you're not confident identifying system files from malicious files, run an automated scan with Combo Cleaner and Windows Defender and stop there - that path catches the vast majority of consumer trojans without the risk of breaking Windows by deleting the wrong file.
Frequently Asked Questions (FAQ)
My computer is infected with Horabot malware, should I format my storage device to get rid of it?
There are alternative methods to remove Horabot without formatting your device, such as using a trusted antivirus solution.
What are the biggest issues that malware can cause?
Some of the biggest issues include unauthorized access to sensitive information, such as personal and financial data, leading to identity theft or financial loss. Additionally, malware can disrupt system operations, encrypt data, cause system crashes, and other problems.
What is the purpose of Horabot?
The purpose of Horabot is to facilitate phishing attacks. It is designed to gain control over the victim's Outlook (or another) mailbox, extract email addresses from contacts, and send phishing emails with malicious HTML attachments to all addresses within the victim's mailbox.
How did Horabot infiltrate my computer?
Horabot infects computers through phishing emails with deceptive attachments, leading the victim through URL redirections to an attacker-controlled HTML page. From there, the malware is downloaded and executed, compromising the victim's system.
Will Combo Cleaner protect me from malware?
Indeed, Combo Cleaner has the ability to remove nearly all known malware. However, it is important to note that sophisticated malware often conceals itself deeply within the system, necessitating a comprehensive system scan to ensure thorough detection and removal.
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Tomas Meskauskas
Expert security researcher, professional malware analyst
I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats.
PCrisk security portal is brought by a company RCS LT.
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