How to remove Squidoor backdoor malware

What kind of malware is Squidoor?

Squidoor is a backdoor-type malware that targets Windows and Linux OSes (Operating Systems). Programs within this classification open "backdoors" into targeted machines to prep them for further infection, and some can even download/install payload malware.

Squidoor has been around since at least the spring of 2023. This malicious program has been utilized in cyber-espionage campaigns targeting entities in governmental, defense, education, telecommunication, and other high-sensitivity spheres throughout Southeast Asia and South America. There is some evidence linking this activity to a threat actor based in China.

Squidoor malware overview

Squidoor is a high-end backdoor designed with a particular emphasis on stealth. This malware has been observed infiltrating devices by exploiting vulnerabilities in IIS (Internet Information Services) servers.

Following the initial infiltration, Squidoor deploys multiple web shells that serve as persistent backdoors and enable attackers to maintain access and control. Successful self-proliferation by this program into different servers is likewise reliant on web shells.

Squidoor has anti-detection and anti-analysis capabilities, such as detecting when executed on a virtual machine or in sandbox environments. It utilizes persistence-ensuring mechanisms, such as setting itself as a scheduled task.

Interestingly, this malicious program uses many methods for connecting to its C&C (Command and Control) server – ten for Windows and nine for Linux OSes. Tunneling via DNS (Domain Name System) or ICMP (Internet Control Message Protocol), and Microsoft Outlook – are just a few of the tactics for C&C connection on Windows.

Squidoor is a modular malware that can move laterally through networks, execute arbitrary commands, gather device data, search directories and files, exfiltrate (steal) files, list running processes, operate as an injector trojan (i.e., inject malicious code into processes/software), and download/install additional malware and malicious content.

Basic device data extracted include: OS details, device name, username and type (privileges), IP addresses, and so on. Squidoor can communicate and send commands to its modules. Known ones had the ability to execute arbitrary commands, execute PowerShell scripts (without relying on powershell.exe binary), introduce (upload) files, delete files/data, and steal specific files.

As mentioned in the introduction, this backdoor has been used in campaigns targeting critical industries and sensitive organizations. In these attacks, the malware was used to collect data on the operation of the targeted entities and key officials/personnel.

It must be mentioned that malware developers often improve upon their software and methodologies. Therefore, potential future iterations of Squidoor can have additional/different features.

To summarize, the presence of software like Squidoor on devices can lead to multiple system infections, severe privacy issues, financial losses, and identity theft.

Threat Summary:

Name	Squidoor malware
Threat Type	Trojan, backdoor.
Detection Names	Combo Cleaner (Trojan.GenericKD.75928811), Fortinet (PowerShell/Squidoor.A!tr), Ikarus (Win32.Outbreak), Kaspersky (Trojan.PowerShell.Agent.ang), Microsoft (Trojan:Win32/Alevaul!rfn), Full List Of Detections (VirusTotal)
Symptoms	Trojans are 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, malicious online advertisements, social engineering, software 'cracks'.
Damage	Stolen passwords and banking information, identity theft, the victim's computer added to a botnet.
Malware Removal (Windows)	To eliminate possible malware infections, scan your computer with legitimate antivirus software. Our security researchers recommend using Combo Cleaner. ▼ Download Combo Cleaner To 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 read more.

Backdoor-type malware examples

We have written about numerous malicious programs; EagerBee, TorNet, SlowStepper, and InvisibleFerret are just a few of our latest articles on backdoors.

Malware is a broad term that encompasses programs with various capabilities. It is also not limited to its classification/type. For example, data-stealing functionalities are prevalent in all kinds of malware, and stealers are often used in combination with other programs.

It must be emphasized that regardless of how malicious software operates – its presence on a system threatens device integrity and user safety. Therefore, all threats must be eliminated immediately upon detection.

How did Squidoor infiltrate my computer?

Malware is primarily proliferated by relying on phishing and social engineering tactics. When leveraged against high-risk entities, malware campaigns can be incredibly targeted (strongly personalized).

Malicious software is usually disguised as or bundled with ordinary program/media files. They come in various formats, e.g., archives (ZIP, RAR, etc.), executables (.exe, .run, etc.), documents (Microsoft Office, Microsoft OneNote, PDF, etc.), JavaScript, and so on. Merely opening a virulent file can be enough to initiate the infection chain.

The most prevalent malware distribution methods include: malicious attachments/links in spam (e.g., emails, PMs/DMs, SMSes, social media/ forum posts, etc.), drive-by (stealthy/deceptive) downloads, online scams, malvertising, untrustworthy download channels (e.g., freeware and third-party websites, Peer-to-Peer sharing networks, etc.), pirated content, illegal software activation tools ("cracks"), and fake updates.

Furthermore, some malicious programs can self-proliferate via local networks and removable storage devices (e.g., external hard drives, USB flash drives, etc.).

How to avoid installation of malware?

We strongly recommend being vigilant when browsing since the Internet is rife with deceptive and malicious content. Incoming emails and other messages must be approached with care. Attachments or links found in suspicious/irrelevant mail must not be opened, as they can be infectious.

Another recommendation is to download only from official and verified sources. Additionally, all programs must be activated and updated using legitimate functions/tools, as those obtained from third-parties can contain malware.

We must stress the importance of having a dependable anti-virus installed and kept updated. This software must be used to run regular system scans and to remove detected threats and issues. 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.

Instant automatic malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced IT skills. Combo Cleaner is a professional automatic malware removal tool that is recommended to get rid of malware. Download it by clicking the button below:
▼ DOWNLOAD Combo Cleaner By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. To 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 read more.

Quick menu:

• What is Squidoor?
• STEP 1. Manual removal of Squidoor malware.
• STEP 2. Check if your computer is clean.

How to remove malware manually?

Manual malware removal is a complicated task - usually it is best to allow antivirus or anti-malware programs to do this automatically. To remove this malware we recommend using Combo Cleaner Antivirus for Windows.

If you wish to remove malware manually, the first step is to identify the name of the malware that you are trying to remove. Here is an example of a suspicious program running on a user's computer:

If you checked the list of programs running on your computer, for example, using task manager, and identified a program that looks suspicious, you should continue with these steps:

Download a program called Autoruns. This program shows auto-start applications, Registry, and file system locations:

Restart your computer into Safe Mode:

Windows XP and Windows 7 users: Start your computer in Safe Mode. Click Start, click Shut Down, click Restart, click OK. During your computer start process, press the F8 key on your keyboard multiple times until you see the Windows Advanced Option menu, and then select Safe Mode with Networking from the list.

Video showing how to start Windows 7 in "Safe Mode with Networking":

Windows 8 users: Start Windows 8 is Safe Mode with Networking - Go to Windows 8 Start Screen, type Advanced, in the search results select Settings. Click Advanced startup options, in the opened "General PC Settings" window, select Advanced startup.

Click the "Restart now" button. Your computer will now restart into the "Advanced Startup options menu". Click the "Troubleshoot" button, and then click the "Advanced options" button. In the advanced option screen, click "Startup settings".

Click the "Restart" button. Your PC will restart into the Startup Settings screen. Press F5 to boot in Safe Mode with Networking.

Video showing how to start Windows 8 in "Safe Mode with Networking":

Windows 10 users: Click the Windows logo and select the Power icon. In the opened menu click "Restart" while holding "Shift" button on your keyboard. In the "choose an option" window click on the "Troubleshoot", next select "Advanced options".

In the advanced options menu select "Startup Settings" and click on the "Restart" button. In the following window you should click the "F5" button on your keyboard. This will restart your operating system in safe mode with networking.

Video showing how to start Windows 10 in "Safe Mode with Networking":

Extract the downloaded archive and run the Autoruns.exe file.

In the Autoruns application, click "Options" at the top and uncheck "Hide Empty Locations" and "Hide Windows Entries" options. After this procedure, click the "Refresh" icon.

Check the list provided by the Autoruns application and locate the malware file that you want to eliminate.

You should write down its full path and name. Note that some malware hides process names under legitimate Windows process names. At this stage, it is very important to avoid removing system files. After you locate the suspicious program you wish to remove, right click your mouse over its name and choose "Delete".

After removing the malware through the Autoruns application (this ensures that the malware will not run automatically on the next system startup), you should search for the malware name on your computer. Be sure to enable hidden files and folders before proceeding. If you find the filename of the malware, be sure to remove it.

Reboot your computer in normal mode. Following these steps should remove any malware from your computer. Note that manual threat removal requires advanced computer skills. If you do not have these skills, leave malware removal to antivirus and anti-malware programs.

These steps might not work with advanced malware infections. As always it is best to prevent infection than try to remove malware later. To keep your computer safe, install the latest operating system updates and use antivirus software. To be sure your computer is free of malware infections, we recommend scanning it with Combo Cleaner Antivirus for Windows.

Frequently Asked Questions (FAQ)

My computer is infected with Squidoor malware, should I format my storage device to get rid of it?

Malware removal rarely requires formatting.

What are the biggest issues that Squidoor malware can cause?

Malware posed threats depend on its capabilities and the attackers' modus operandi. Squidoor opens a "backdoor" to machines – it can cause chain infections, move laterally through networks, collect sensitive data, etc. Hence, this program can cause multiple system infections, serious privacy issues, financial losses, and identity theft.

What is the purpose of Squidoor malware?

Squidoor has been observed being used for cyber-espionage in suspected geopolitically-motivated attacks. However, it could be used for other purposes as well. The most prevalent motivation is financial gain. Yet malware can also be used to amuse the attackers, carry out personal vendettas, disrupt processes (e.g., websites, services, organizations, companies, etc.), and engage in hacktivism.

How did Squidoor malware infiltrate my computer?

Malware is mainly spread through drive-by downloads, online scams, spam mail, malvertising, dubious download sources (e.g., freeware and third-party websites, P2P sharing networks, etc.), illegal software activation tools ("cracks"), pirated content, and fake updates. Some malicious programs can even self-proliferate via local networks and removable storage devices.

Will Combo Cleaner protect me from malware?

Combo Cleaner is capable of detecting and eliminating almost all known malware infections. It must be mentioned that performing a complete system scan is essential since sophisticated malicious programs tend to hide deep within systems.

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