Defined by their ability to self-replicate, computer viruses are a serious concern for businesses. If one of the computers connected to your business’s information technology (IT) infrastructure becomes infected with a virus, it may spread to other connected computers. The virus will essentially replicate itself as it spreads to other devices, thereby compounding the damage it causes. Computer viruses, however, can be classified as resident or non resident, depending on their method of operation.

What Is a Resident Computer Virus?

A resident computer virus is a type of computer virus that’s deployed and resides within a computer’s random access memory (RAM). All computers contain RAM. Not to be confused with a hard-disk drive (HDD) or solid-state drive (SSD), RAM consists of memory sticks that allow a computer to read and write data in any order. If a virus lives within a computer’s RAM, it’s considered a resident computer virus.

What Is a Non-Resident Computer Virus?

A non-resident computer virus, on the other hand, is a type of computer virus that doesn’t reside within a computer’s RAM. Non-resident computer viruses can still be deployed within RAM, but they don’t stay there. Rather, shutting down the computer will typically erase the RAM, which subsequently stops the non-resident computer virus from being executed.

Why Resident Computer Viruses Are More Harmful

Both resident and non-resident computer viruses can cause a world of heartache for you and your business, but the former is particularly a concern. Non-resident computer viruses are executable. Therefore, unless a non-resident computer virus is set to run on startup, shutting down or restarting your computer will stop it.

The only way for a non-resident virus to carry out its malicious effects is through execution. In comparison, resident computer viruses don’t require manual execution. A resident computer virus will stay within your computer’s RAM where it’s able to perform its malicious activities at any time. As long as your computer is running, it will use RAM, in which case the resident computer virus will remain active.

Some types of resident computer viruses are designed to quickly spread, in which case they can infect other computers or devices on your business’s network in a short period.

To make matters worse, resident computer viruses are oftentimes difficult to remove. Since they embed themselves into RAM, traditional antivirus software may fail to catch them. There are, however, special types of antivirus software that are designed to detect, as well as remove, resident computer viruses.