What Is Polymorphic Virus? How to Detect & Prevent It?

Written By Sambita Panigrahy  
Anuraag Singh
Approved By Anuraag Singh 
Published On October 13th, 2023
Reading Time 8 Minutes Reading

Polymorphic virus in cybersecurity is a sophisticated file-infecting agent that may alter copies of themselves to evade detection while keeping the same fundamental functions after each infection. Polymorphic viruses change the structure of their physical file after each infection by encrypting their codes and using different encryption keys each time.

Every time they infect a machine, polymorphic viruses use mutation engines to change their decryption procedures. Because they don’t use a static, unchanging code in this manner, conventional security methods could be unable to easily detect them. They become even more evasive to detection due to the usage of sophisticated mutation engines that produce billions of decryption routines.

History of Polymorphic Virus

The first polymorphic viruses appeared in the 1990s as a result of a research study to highlight the shortcomings of the then-current antivirus scanners. The first, a virus known as 1260, or V2PX, was designed to warn internet users, but because of the virus’s capabilities, it unintentionally sparked a surge of criminal behavior. Many polymorphic viruses appeared throughout the years that followed, and today almost every malware infection incorporates polymorphism in some way.

Often, polymorphic viruses are spread by spam, infected websites, or other malware. Some of the most well-known polymorphic viruses in existence include URSNIF, VIRLOCK, VOBFUS, and BAGLE or UPolyX. Polymorphic viruses put their victims at much greater risk when paired with other malicious practices. In March 2015, researchers found that VIRLOCK had changed to add ransomware routines, making it challenging to locate and remove.

Examples of Polymorphic Viruses

The most well-known instances of polymorphic malware and viruses include:

Example 1 – The Storm Worm: A multi-layered attack, The Storm Worm tricked users into downloading a trojan through social engineering techniques. The malware subsequently infected the computer and turned the target’s system into a bot. The campaign affected hundreds of thousands of users’ access to the internet at once while infecting over 1 million endpoints.

Example 2 – VirLock: This malicious attack, which is propagated via shared programs and cloud storage, is regarded as the first instance of polymorphic ransomware. It acted like traditional ransomware, preventing the victim from accessing the endpoint and changing files until a ransom was paid.

Example 3 – Thousands of computers worldwide were taken over by Beebone, an advanced polymorphic malware attack, to create a botnet with the intention of interfering with banking transactions.

Example 4 – Cryptowall: It is a type of polymorphic ransomware that is famous for encrypting users’ computers. The main idea behind using this is to extract a good ransom amount in return for the decryption code. 

How Does Polymorphic Virus Work? Understand Its Nature

This procedure is frequently followed by a polymorphic attack:

  • By using encryption to conceal the harmful code, the cybercriminal can get beyond the majority of conventional security measures.
  • The infected file is downloaded and decrypted after the virus has been installed on an endpoint.
  • Even if a previous version of the computer virus had been discovered and added to a blocklist, a mutation engine attaches a new decryption routine to the virus after it has been downloaded, making it appear to be a different file and rendering it unrecognizable to security programs.

Although polymorphic viruses may change in terms of their file name, size, or location, the malware’s operation, purpose, and function never change. For instance, a trojan with polymorphic traits will always function as a trojan, even if the signature changes.

How Can You Detect a Polymorphic Virus?

Because of their powerful mutation capabilities, polymorphic viruses — or any sort of malware that uses polymorphic techniques — can be challenging to identify by conventional threat detection approaches.

In simple words, standard antivirus or antimalware software scans a file for code sequences called signatures or heuristics. Once data has been re-encrypted, these instruments are unable to detect the threat. Even if a known polymorphic virus that has been added to the blocklist has already infected another endpoint on the same network, this is still true.

Businesses must adopt cutting-edge cybersecurity solutions that support signature-less malware protection to detect polymorphic infections.

Best Practices to Prevent Polymorphic Viruses

Polymorphic virus attacks usually begin with a user-level intrusion. All internet users must, therefore, behave responsibly and be on the lookout for symptoms of an attack.

Typical advice includes:

  • Install a dependable cloud-native next-generation antivirus program on your PC, and make sure it gets frequent updates.
  • Both your operating system and your software should be updated.
  • Use a pop-up blocker or refrain from clicking pop-up adverts.
  • Never open email attachments that are unsolicited or suspicious from unknown senders.
  • Never connect to an insecure Wi-Fi network.
  • Only click links that begin with HTTPS.
  • Free software should always be used responsibly and with a thorough understanding of the rules and restrictions.
  • Your smartphone’s screen should be locked.
  • Use strong passwords throughout the board.
  • Enable multi-factor authentication on all hardware and software.
  • The rights you grant to apps when you install them should all be carefully reviewed.
  • Be cautious while authorizing website cookies.

How to Avoid Polymorphic Virus from Entering Your Device?

Here are some of the means you can try to avoid it from harming your devices.

Refresh Your Defenses

Having the proper security solution software in place is one of the simplest ways to safeguard your system from aggressive, adaptable code. The capacity to use a considerably wider variety of scanning techniques, tools, and algorithms to recognize and address a much wider range of threats is one advantage that high-quality antivirus solutions have over simple versions. Also, it defends against a wider range of potential vulnerability points, including Internet downloads and email attachments, that could provide access to your machine.

Dealing with a Changing Threat

A security solution’s failure to recognize the infection’s new state once it replicates is frequently the main issue when attempting to combat the threat posed by polymorphic malware. Security software typically “blocklist” viruses once they are discovered, and anything that resembles or behaves like one is consequently automatically prohibited. This is made challenging by polymorphic code, which frequently alters itself. Its new form could get past defenses that no longer identify it even after being repulsed.

Packages of comprehensive security solutions combat this in two ways:

  • Heuristic Scanning: A heuristic scan increases the likelihood of finding and halting a new variant of the virus by looking for some key components that the threat may share rather than searching for an exact match to a previously detected danger.
  • Behavior-based Detection: This kind of antiviral feature examines a virus’s behavior rather than just its code.

Be Aware of Threats via the Internet and Email

The best defense against the spread of polymorphic viruses is vigilance. A machine is frequently initially infected as a result of an action like downloading an infected email attachment or going to a website that has been compromised. Your first and greatest line of defense is frequently your own sound judgment.

  • Email Caution: Avoid visiting dubious websites and refrain from opening attachments you didn’t request. Never open an email from a sender you are unfamiliar with.
  • Software Caution: Before downloading any software or updates, be sure it has been virus-scanned. It’s also preferable to download from a reliable source directly rather than from links or other websites.

Maintain Software Updates

While hackers are always updating and improving their codes, good men are doing the same on your behalf. The corporations that own those systems try to address any faults and vulnerabilities that arise when hackers build code intended to exploit flaws and vulnerabilities in operating systems and software. Free software patches are used to patch up outdated software. Make careful to quickly install them.

Consider Security a Priority

Your defenses must continue to advance as polymorphic viruses get more complex. Avoid becoming stale. Ensure sure the passwords on your system and accounts are complex. It won’t do to use your mother’s maiden name.

Change passwords occasionally, but not all the time. A UNC study conducted for the Federal Trade Commission found that changing passwords too frequently may be harmful since people frequently just modify their existing passwords in predictable ways. It is preferable to develop complicated passwords that are challenging for an attacker to guess as opposed to often changing a simple password. Never use the same password on several systems or accounts, as well.


Q- Can antivirus software detect polymorphic viruses?

Detection of polymorphic viruses using traditional antivirus software can be challenging. However, advanced antivirus applications that support behavior analysis may identify this virus.

Q- What are the signs of having a polymorphic virus on your device?

Pay close attention to unusual system behavior, slow performance, unexpected pop-ups, or frequent crashes. Thus, make sure to run a full scan to avoid such situations.

Q- Is creating the polymorphic virus illegal?

Creating this virus is strongly discouraged since it may lead to legal consequences. However, cyber security experts and ethical hackers use it in a controlled environment for non-malicious and testing purposes.