Why Might Anti-malware Software Not Detect Malicious Software?

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Why Might Anti-malware Software Not Detect Malicious Software?

If a program encrypts or hides within another file, malicious software can slip past automated scanners. 

This can be done by scattering components on disk and throughout memory that the malware will piece together when executed. Another type of evasion involves dynamically generating code (or decoding encrypted code) on the fly such that no part of the source code exists in the executable until run time. 

Additionally, some malicious may cause antivirus software to shut down or prevent it from running by tampering with the system’s registry, preventing updates to the application.

How Malware Bypasses Anti-Malware Software?

The primary technique used to bypass anti-malware software is packers or packing, which “packages” the malware into an executable that masks malicious behaviour in something innocuous. Packing methods are often very simplistic. 

For example, some malware is compiled without any sections (a section is a block of code with permissions set to execute) or resources (data embedded in the executable to make it larger, used by the loader to resolve external references) not bound to a valid import table. 

Other techniques include removing debug information from binaries, carefully choosing which symbols are stripped, using string obfuscation algorithms for packer strings, self-modifying code, or anti-debugging techniques.

Non Uniform Signature

Malicious software does not have a uniform signature that anti-malware programs can detect. Some malicious software might not show up in virus or spyware definition updates because it has not been seen before. Even if it is detected, some malware may not be adequately recognised because of its obfuscation techniques. 

Anti-malware software that does detect the malware may not always be able to clean it or eradicate it if the infection is somehow made “inoperable”.

Additionally, some malware can show tests for specific antivirus software but may not show any detection in other tests. Many antivirus software companies do not share their detection rules and algorithms, so products from different vendors will also detect different variants of the same malware.

Rootkits and Bootkits

Another common technique to evade antivirus software is to use rootkits and bootkits, which insert malicious drivers and services deep into the system. These hide low-level malware components from higher-level software, for example, by intercepting system calls or function requests sent to operating system libraries.”

Malware may also disable or alter the functionality of security products. For example, many ransomware pieces terminate antivirus software after encrypting a computer’s files.

Drawbacks Of Anti-Malware Not Detecting Malware

The fact that anti-malware software is not 100% effective in detecting all malicious software means there are plenty of opportunities for malware infections to slip past security systems. Even if the malware is detected, it is often not obliterated or blocked from future installation. This can be since the complete removal of some malware is impossible without damaging essential system files.

Additionally, anti-malware programs do not perform 100% of the time. If they are executed or installed incorrectly, they may also fail to detect malware.

However, even if anti-malware software fails to prevent infection, it serves as another defence against these malicious programs by providing alerts and notifications on system changes that indicate suspicious activity. It also provides log files and other information about the infection that can assist in malware removal.

What Can Be Done To Stop Malware?

The best way to prevent infection is to be especially cautious when installing software. Carefully reading the license agreements and terms of use before installing or permitting installations can help avoid the unintentional installation of malware. Don’t download pirated copies of commercial software, often infected with malware to damage the creator’s profits.  

It is also essential to make sure all software installed on a computer has up-to-date security patches and bug fixes. This can prevent the installation of malware that might otherwise exploit unpatched vulnerabilities in older software.

If a computer is already infected, having good quality anti-malware software installed can help detect and remove any piece of malicious software. Anti-malware software can also be used to help determine if the malware was able to carry out its intended functions before removal. If it was, this might indicate other pieces of malware or even rootkits still present on the computer.

The best way to prevent an infection is to run anti-virus, anti-spyware, and firewall software on your computer:

  • Anti-virus: Scans your hard disk for any viruses.
  • Anti-spyware: Scans your computer’s memory and hard drive for spyware, adware, or other malicious software that can track personal information about you without your knowledge.
  • Firewall: Security software that protects against hackers who attempt to access your computer from the Internet.
  • Software updates: Install all available software patches and updates provided by your operating system or applications vendor.
  • Reasonable passwords: Use strong, unique passwords for each of your important accounts, especially email and banking accounts. Be sure to change these monthly at least, but make them challenging enough that they would be difficult for someone to guess.
  • Backups: You must regularly create backups of your data. If malware infects your computer, you can restore the infected files from backup, knowing your originals are safe and sound (hopefully).
  • Browsers: Keep your browser up to date by enabling automatic updates if available.
  • -Email safety: Email attachments are one of the significant ways malware spreads, so be very cautious downloading attachments or opening email messages from unknown senders.
  • Avoid P2P sites: Downloading software illegally is typically how people pick up malicious software like viruses, spyware and other harmful programs.


Since Malware was not present initially on disk for security applications to detect, these examples of evasion techniques make it difficult for anti-malware applications to perform their function of detection and disinfection. These specific types of obfuscation and encryption are typically not published and require some reverse engineering.

Prevention from Malware relies on the user’s pattern of life. Avoid suspicious sites and do not download any software from unknown sites.

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