How Computer Viruses Are Spread

There are few situations that are worse than when you have work to do or some form of research to perform, you sit down comfortably in front of your personal computer, and then you are suddenly overwhelmed with anti-virus alerts or even worse, a screen locker virus that is preventing you from accessing anything on your computer. And it may even encrypt your data and hold it for ransom. As unbelievable as that sounds, we encounter trojans and viruses that perform those crippling functions several times a week. Computer viruses infect both systems with current anti-virus software installed and also unprotected computers. Obviously, unprotected computers are a lot more likely to get compromised by a virus than protected systems.

There are numerous ways that computer viruses are spread from one computer to another. And a lot of computer users lack a clear understanding of how computer viruses are spread. both online and offline. Today we’ll be covering some of the most frequent and popular computer viruses spreading techniques in use today. Most of the techniques have been in use for many years, while others are gaining in popularity.

Email Attachments and Malicious Embedded Website Links

Most computer users became familiar with the high occurrences of email attachments carrying viruses many years ago. Back in the early days of Microsoft Outlook Express, the email client would automatically open email attachments, with little user input. Now the email clients don’t automatically open accompanying attachments and the mail preview option can be disabled. And since those changes were put into place, computer viruses spreading through email messages have decreased. They definitely haven’t stopped, but they have decreased. Today users still receive infected attachments with messages, but most of the time they make a mistake and open the attachments because the message was supposedly sent from someone that they know and with a title that got them curious about what the attachment contained.

Computer Networks

If your computer is connected to a home network or it’s part of a workgroup or domain, your computer could acquire a virus without you being at fault. Another person in your home or office employee at your job could unknowingly download an infected file and then quickly spread it throughout your entire home or office network in a very short time, causing slowdowns, data corruption, and possibly data loss. You should always have a reputable anti-virus installed and updated on any computer that you use. And if your computer is on an office network that is administered by professional Information Technology staff, you’re probably covered. But keep in mind that no anti-virus utility can stop every computer virus. They might slow them down a bit, depending on the trojan or virus, but they still can’t stop them all. And in a great deal of the situations that we come across out in the field, the installed anti-virus can’t even manage to remove the infection once it’s taken hold of a computer that was protected with the anti-virus utility to start with.

Infected Computer Software

There are countless games, productivity software packages, web browser add-ons, high-definition video, and high-quality audio files available online for download. And a great deal of those are free. Unfortunately, even though they may claim to be free, they may have strings attached. Many of those free programs include malicious files that were intentionally added to help pay for the work that was put into creating those applications and games. While other online software files are infected with trojans without the software creator’s consent or approval. The best practice used to be to only download software from trusted sources, such as Cnet, but now many of the original trusted sources can no longer be trusted because they’re offering files for download that contain malicious files. It all boils down to advertising and profits. Many of the online download sites will provide access to free and shareware files, but those files may contain adware that can be almost as irritating as ransomware in some cases. One of the best practices to use when downloading files online is to carefully read the software user agreements. If they mention anything about containing advertising software that will monitor your online activities and then display advertisements based on those activities, then the software should be avoided. Also never select the “Express Installation” or “Recommended” installation options when you install downloaded software, because in many situations you may be unknowingly consenting to installations of browser add-ons and toolbars, system utilities, and also entire web browsers that you have no use for. Always select the “Custom Installation” option, so you’ll have the choice to minimize any unneeded software installations and add-ons.

Fake Programs/Trojans

Rogue programs such as fake anti-virus and security utilities are one of the most frequent ways that online users acquire computer viruses today. It’s very irritating to download a program that you think will help keep your computer data safe, when in fact the fake anti-virus software that you download and install is actually exactly what you’re trying to protect yourself against. You may come across rogue software advertisements on malicious websites and also on legitimate websites that participate in compromised ad networks. Unfortunately, even some of the best and most secure websites advertise rogue software programs displayed over ad networks. In most cases, the advertisements are taken down quickly by the site administrators, if it’s a legitimate site, while the flat out malicious websites may run the rogue advertisements continuously around the clock. And depending on the traffic that the websites receive during the time that the malicious software advertisements are being displayed, large amounts of site visitors may be infected. Depending on the exploits being utilized by the fake anti-virus utility advertisements, many of the visitors to those sites may acquire an infection even though they never actually clicked on the malicious advertisements, because the viruses were installed through the use of drive-by installation techniques.

Infected Websites

Unsuspecting online users may become infected with computer viruses, trojans, and also ransomware from intentionally malicious websites and also websites that have been compromised. Depending on the currently installed operating system and also the installed software on a website visitor’s system, drive-by installations of malicious software can easily occur. While visiting a malicious website, without warning malicious programs can be installed on visitors’ computers without their consent or input. Microsoft Windows systems are the primary target of this type of attack. Other popular applications may also be the target of an attack, such as Sun Microsystem’s Java, Microsoft Internet Explorer web browsers, the Adobe Reader, and many other applications. The best defense for this type of attack is to:

  1. Keep your operating system updated.
  2. Keep your applications updated with the latest updates.
  3. Install reputable anti-virus, keep it updated and also perform weekly full system scans.
  4. Install a strong firewall with Windows process control to prevent malicious software from taking hold of your system. The built-in Windows firewall isn’t enough to keep your system secure.
  5. Never click on security-related advertisements, prompts for web browser updates, or prompts for the installation of video players needed to view online content. Only download your software from trusted sources. And always choose the “Custom Installation” options of applications so you can avoid the unwanted adware and other junkware that may be included with free downloadable programs.
  6. USB Flash Drives and Other External Media. Sharing and transferring files on flash drives is a very common practice today. The little devices hold a lot of data, they’re small, and also easy to transport. But unfortunately, those external drives can easily be compromised and loaded with malicious files that will infect the computers that the drives are connected. Because of that vulnerability, Microsoft issued software patches that disabled the auto-play feature of Microsoft Windows.
  7. Another area of concern involving malicious external devices involves smartphone chargers. Earlier this year three researchers at the Georgia Institute of Technology demonstrated how easily smartphones running the latest version of Apple IOS could be compromised by a malicious charger that installed malware on the smartphones in a matter of seconds once they were connected to the devices.
  8. Keep in mind that smartphones are just tablet personal computers that we can make telephone calls on. They’re just as vulnerable to computer viruses as your desktop computer. New forms of malware are being discovered daily that compromise smartphones. So for additional protection, install a reputable mobile anti-virus program on your smartphone to help protect your device from external threats such as malicious programs and text messages.