How do computer viruses spread over the network

My house has multiple computers usually a few are connected to the internet and running at a time all connected to the internet through a Linksys ethernet router. Hypothetically, if two computers were connected to the internet, and one of them contracted a virus or two, would the virus be able to get to the other computers connected to the router more easily?

Your setup sounds very much like my own. Several computers, most are always on, and all sharing a connection to the internet. Become a Patron of Ask Leo! Behind your router, all your computers were exposed to each other without a firewall. The good news is that most viruses that can move easily from machine to machine without human intervention are exactly those that routers are great at stopping in the first place. So the risk of exposure is actually pretty low.

The real risk is from other viruses that more typically cross the router via other means — like email. Obviously routers and firewalls allows email to cross. More likely is that the infected machine will simply start to send email with infected attachments at a rapid rate. Less clear are things like malicious activex controls and other web based virus attack vectors, instant messaging viruses and more. In this scenario your computer has been infected with a virus that records information from your computer and transmits that information back to the virus creator or host machine.

Then the virus transmits that information to the host computer. In some cases viruses are created and distributed purely for the satisfaction of the programmer that created it. The more computers that get infected by the particular virus the more sense of accomplishment the programmer can claim.

In the case of viruses that provide remote access to your computer, this may not necessarily be full access to your computer but rather can slave your computer to the host machine which may send your computer commands to perform actions that benefit the virus programmer in some way. In the event that there are hundreds or even thousands of computers infected and they are all sending junk data to a 3rd party, this causes the 3rd party site to become flooded and no longer functions normally.

So the programmer of the virus may be a member or a competing organization with the 3rd party and since their virus is infected on several various unrelated workstations there is virtually no way to tie the flooding of the website or network to the programmer who created the virus. Now there are viruses that actually damage your computer or are created to spread from computer to computer over a network and once in place, they search out the operating system and corrupt or delete specific files.

These types of viruses are usually created by a programmer with an opposite agenda then the organization the programmer has infected with the virus. These kinds of viruses spread very well over email since most organizations send lots of emails internally, but in such scenarios this can infect computers even outside the organization and so individuals who were not even targeted become collateral damage.

In any case viruses for the time being are here to stay. At least until we can put a stop to smart people willing to benefit themselves at the expense of others. Please submit exemption forms to accounting interworks. InterWorks uses cookies to allow us to better understand how the site is used. By continuing to use this site, you consent to this policy.

Review Policy OK. Because many viruses include a logic bomb — code that ensures that the virus's payload only executes at a specific time or under certain conditions — users or admins may be unaware that their applications are infected and will transfer or install them with impunity. Infected applications might be emailed inadvertently or deliberately — some viruses actually hijack a computer's mail software to email out copies of themselves ; they could also be downloaded from an infected code repository or compromised app store.

One thing you'll notice that all of these infection vectors have in common is that they require the victim to execute the infected application or code. Remember, a virus can only execute and reproduce if its host application is running!

Still, with email such a common malware dispersal method, a question that causes many people anxiety is: Can I get a virus from opening an email? The answer is that you almost certainly can't simply by opening a message; you have to download and execute an attachment that's been infected with virus code.

That's why most security pros are so insistent that you be very careful about executing email attachments, and why most email clients and webmail services include virus scanning features by default. A particularly sneaky way that a virus can infect a computer is if the infected code runs as JavaScript inside a web browser and manages to exploit security holes to infect programs installed locally.

Some email clients will execute HTML and JavaScript code embedded in email messages, so strictly speaking, opening such messages could infect your computer with a virus. But most email clients and webmail services have built-in security features that would prevent this from happening, so this isn't an infection vector that should be one of your primary fears.

Symantec has a good breakdown on the various types of viruses you might encounter , categorized in different ways.

We've already met resident and non-resident viruses , boot sector viruses , web scripting viruses , and so on. There are a couple other types you might want to be aware of:. Keep in mind that these category schemes are based on different aspects of a virus's behavior, and so a virus can fall into more than one category. A resident virus could also be polymorphic, for instance.

Antivirus software is the most widely known product in the category of malware protection products. CSO has compiled a list of the top antivirus software for Windows , Android , Linux and macOS , though keep in mind that antivirus isn't a be-all end-all solution. When it comes to more advanced corporate networks, endpoint security offerings provide defense in depth against malware. They provide not only the signature-based malware detection that you expect from antivirus, but anti-spyware, personal firewall, application control and other styles of host intrusion prevention.

Gartner offers a list of its top picks in this space , which include products from Cylance, CrowdStrike, and Carbon Black. One thing to keep in mind about viruses is that they generally exploit vulnerabilities in your operating system or application code in order to infect your systems and operate freely; if there are no holes to exploit, you can avoid infection even if you execute virus code.

To that end, you'll want to keep all your systems patched and updated, keeping an inventory of hardware so you know what you need to protect, and performing continuous vulnerability assessments on your infrastructure. How can you tell if a virus has slipped past your defenses? With some exceptions, like ransomware, viruses are not keen to alert you that they've compromised your computer. Just as a biological virus wants to keep its host alive so it can continue to use it as a vehicle to reproduce and spread, so too does a computer virus attempt to do its damage in the background while your computer still limps along.

But there are ways to tell that you've been infected. Norton has a good list ; symptoms include:.