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Hackers design malicious code to sneak into your computer, squat inside your programs, and steal your information. Learn about the different types of malicious code, how to spot them, and how to limit the damage done. Then, install powerful antivirus software like Avast One to help flush out malicious code and keep your device better protected.
The catch-all malicious code definition is any computer coding or web scripting designed to create security holes and cause damage to computer files. Malicious code can open secret backdoors inside Java applets, browser plug-ins, and many other programs to allow unauthorized access to cybercriminals, which can lead to data theft, spying, or even the complete takeover of applications.
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Despite sharing broad overlaps, malicious code and malware are not one and the same. While ransomware and other forms of malware fall under the umbrella of malicious code, not all malicious code is malware.
Malicious code refers specifically to any code or scripts that can cause harm, regardless of whether they’re packaged as standalone software, like typically malware, or hidden within another program, like a logic bomb that will impact only if a certain condition is met.
Malicious code attacks can compromise systems, steal data, or cause disruption, often in subtle or covert ways. Some malicious code is visible and can be detected relatively easily, while other harmful code like backdoors or logic bombs can operate stealthily, remaining hidden for extended periods until certain conditions are met or actions are taken.
Here are some of the most common malicious code types:
VirusesIll-intentioned coders can write malware code for computer viruses that activate when you click an infected link, open an email attachment, or visit a compromised web page. Once activated, the malware can spread to other systems connected to the infected host, including those closest to you. For example, the infamous Melissa email virus in 1999 rapidly spread to the first fifty contacts in the address book of anyone who opened the infected email
Trojan horseTrojan horses are seemingly legitimate computer programs or files, with malicious code hidden within. For example, the Emotet trojan was planted inside Microsoft Word documents and spread rapidly. The trojan was then rented out to other cybercriminals to target new unsuspecting victims.
Trojans are relatively easy to write, making them accessible even to beginners looking to practice their coding skills. If your computer starts behaving unusually, it's wise to use a trojan remover to check for any hidden threats. And remember, creating and distributing malware is illegal and carries serious consequences.
SpywareMalicious code can also function as spyware, embedding itself within your favorite programs to monitor and capture sensitive information. It can quietly wait for valuable data, like passwords or bank account details, and send this information to the attacker once it's detected.
Thankfully, you can usually remove spyware if it ever infects your system.
WormsA computer worm contains malicious code that can spread through an entire network and take over critical files before being noticed. In 2017, the WannaCry ransomware worm locked millions of Windows files under encryption until a ransom was paid in cryptocurrency. To help ensure your system remains protected from covert threats, regularly use a malware removal tool to scan for worms.
Backdoor attacksBackdoor attacks are examples of malicious code that don’t fall under the “malware” label. Imagine someone secretly accessing your home without your knowledge because of a flaw in your lock that allowed it to be picked easily — that’s what a backdoor attack is like.
Hackers can sneak through backdoors in software to gather sensitive info, steal financial details, or even commit identity theft. Backdoors also let hackers erase crucial files to damage a system, and offer a pathway to infect other systems.
Scripting attacksScripting attacks, such as cross-site scripting (XSS), use malicious scripts to change how programs operate. Similar to an SQL injection, a malicious script inserted into a program can reroute data to and from cybercriminals.
For example, rather than searching a secure database for your username and password, a malicious script can redirect the query to the hacker’s database, granting them unauthorized access to your account. Malicious scripting can also alter web pages to send information you may enter, like online banking details, directly to the hacker's computer. In 2019, Fortnite suffered a scripting attack that allowed hackers to log into user accounts without a password.
Browser attacksSome malicious code targets web browsers to exploit vulnerabilities and compromise user data. It can appear as malicious scripts, drive-by downloads, or deceptive ads, often infiltrating via compromised websites. Once active, it may steal sensitive information, track browsing activities, or redirect users to harmful sites. If your browser is hijacked, removing the malicious code can help restore its normal function.
Malicious code attacks are — by nature — sneaky. So, if it’s so hard to detect, how can you tell if malicious code’s running?
Here are a few red flags that may indicate the presence of malicious code:
Erratic performance: If you’re experiencing endless pop-ups, windows opening up, or programs unexpectedly shutting down or freezing a lot, malicious code could be trying to run dangerous software.
Frequent system crashes: If your computer is crashing frequently, malicious code could be interfering with your operating system.
Unauthorized home page changes: Malicious code may have altered your browser settings to redirect you to harmful or unwanted websites. A browser cleaner tool can help you reclaim your homepage.
Strange startup programs: Unfamiliar programs automatically starting during boot-up can be an indication that malicious code is embedded in your system and running in the background without your knowledge. Check your startup programs and remove anything you don’t remember installing.
Frequent pop-ups, erratic performance, and strange programs appearing on startup are all potential signs of a malicious code infection.
If you think malicious code has infected your machine, take the following steps to help address the problem:
Disconnecting the impacted device from the internet can help limit malicious code from spreading further while you continue to troubleshoot the problem. An IT specialist can help you reconnect safely and better diagnose the traffic coming in and out of your system. They can also put malicious code protection mechanisms in place to limit the damage and spread.
There’s no telling who malicious code has sent your details to. Create new, strong passwords to be safe, and set up two-factor authentication (2FA) to place an extra layer of protection on your online accounts. This way, even if the hacker has access to your password, they’ll still need access to your email or phone, and biometric data to sign in.
Use reliable antivirus software to help remove the malicious code and protect your device from future attacks. If the code is particularly sneaky or stubborn, there’s a chance your antivirus software won’t flag it as malicious code. In that case, you may need to restore your operating system from a backup made before the problems started. That should wipe all traces of the malicious code from the programs or files it’s hiding in.
Then, after securing your computer, install a comprehensive online security app like Avast One for extra protection against malicious code and future online attacks.
Whether you want to protect your business, home, or mobile device, it’s important to take a robust, multi-layered approach to defending against future malicious code attacks.
Install a reliable anti-malware tool: An antivirus can help scan for and remove any malware from your computer. It can sniff out malicious code lurking around your favorite programs, warn you if you are doing something dangerous, and update itself to stay on top of the latest malicious code attacks.
Get a secure VPN: VPNs help you encrypt your internet connection, browse more safely on public Wi-Fi, and prevent man-in-the-middle hacking attacks and other threats.
Get a pop-up blocker: Learning how to block pop-ups on Firefox and other browsers can be a first line of defense against the types of malicious code that may hide in browser apps.
Get a firewall: A firewall can help screen out threats trying to gain access to your device. The built-in Windows firewall may not respond to all malicious code threats, but it’s better than no firewall at all.
Don’t open unknown items: Don’t open emails from unknown senders. Don’t open attachments you aren’t sure of. Don’t click mysterious links. These simple rules can keep you safer against phishing attachments laced with malicious code while online, on social media, and especially while checking your email.
Keep programs updated: Programs often release regular updates that can patch security holes and shore up vulnerabilities that hackers can find and exploit. Update your programs regularly or enable automatic updates on your device to plug these holes so malicious code can’t get in.
From firewalls and VPNs to ad blockers and software updates, there are many ways to help protect against malicious software.
If you want to see how your cyber awareness stacks up, you can take the Cyber Awareness Challenge 2024, created by the United States Department of Defense. This challenge acts as a training program and test in one. But no matter how well-trained you are, it’s always best to use expert tools to supplement protection against malicious code.
Malicious code can open doors to worms and viruses — Avast One can help close them. Our award-winning software can warn you if an intruder is snooping around, then help kick them out and keep them out. Any infections found are put into quarantine, and if someone tries to change your programs you’ll find out. Throw out hackers and bolt the door behind you with Avast One.