The word "virus" gets used loosely to mean any malicious software — what security professionals call malware. This includes viruses, trojans, spyware, adware, ransomware, browser hijackers, and cryptocurrency miners. Each behaves differently, and each leaves different signs.
The challenge is that many infections are deliberately designed to be invisible. Attackers don't want you to know you're infected — they want to quietly steal your passwords, harvest your banking details, or use your computer's processing power without interrupting your day. That said, even the stealthiest malware usually leaves some trace.
Warning Sign 1: Your Computer Is Suddenly Much Slower
A significant unexplained slowdown is one of the most common early signs of infection. Cryptocurrency miners are particularly notable for this — they use your CPU and GPU at high intensity to mine digital currency for the attacker, consuming resources that should be available to you.
If your computer was running fine and is suddenly noticeably slower, open Task Manager (Ctrl + Shift + Esc) and check what's using your CPU and RAM. If an unfamiliar process is using a large percentage of resources, that's a red flag.
Warning Sign 2: Pop-Up Advertisements
Seeing pop-up ads — especially outside your browser, or when no browser is open — is a classic sign of adware infection. Adware injects advertisements into your browsing experience or generates its own pop-up windows to generate revenue for the attacker. It's rarely dangerous in itself, but it's a sign your security has been compromised and worse threats may also be present.
Warning Sign 3: Your Browser Behaves Strangely
Has your homepage changed without your doing? Is your search engine different from the one you set? Are there new toolbars or extensions in your browser that you didn't install? These are classic signs of a browser hijacker. Browser hijackers modify your browser settings to redirect your searches through systems that generate revenue for attackers — and often collect your browsing data in the process.
Warning Sign 4: Your Antivirus Has Been Disabled
Some sophisticated malware specifically targets and disables security software. If your antivirus has stopped working, won't update, or can't be turned back on, this is a serious warning sign. A well-functioning antivirus shouldn't turn itself off.
Similarly, if you're suddenly unable to access security-related websites (AV vendor sites, Windows Update), malware may be actively blocking them.
Warning Sign 5: Friends Are Getting Emails or Messages You Didn't Send
If your contacts are receiving emails from your address that you didn't send, your email account has been compromised. This could mean your email password was stolen (via phishing or keylogger) and someone is using your account. Change your password immediately on a different, clean device, and enable two-factor authentication.
Warning Sign 6: Ransomware — Files Suddenly Inaccessible
Ransomware is the most immediately dramatic form of malware. Your files become encrypted — you can't open them — and you receive a message demanding payment for the decryption key. If this has happened to you, do not pay the ransom without seeking professional advice first. Some ransomware strains have free decryption tools available; paying just encourages the criminals and doesn't guarantee your files back.
Bring the machine to us immediately. The sooner we act, the better the recovery options.
Warning Sign 7: Unusual Network Activity
Some malware communicates continuously with remote servers — sending your data out or receiving instructions. This shows up as unusual network activity. If your internet connection seems slow, or your router lights are blinking heavily when you're not doing anything, it may be worth investigating what's using your network.
Warning Sign 8: Your Webcam or Microphone Light Activates Unexpectedly
If your webcam indicator light comes on when you're not using video software, this is a serious sign that something may be accessing your camera. Remote Access Trojans (RATs) can activate webcams and microphones to spy on victims. If you see this, disconnect from the internet immediately and bring the computer in for a thorough scan.
What to Do If You Suspect Infection
First, don't panic. Here's what to do:
- Stop using the computer for sensitive tasks — don't log into internet banking, email, or anything containing personal information.
- Run your antivirus — if it's working, run a full scan. Also download and run Malwarebytes Free as a second opinion. Microsoft also offers a free Malicious Software Removal Tool.
- If antivirus found nothing but you still suspect infection — some sophisticated malware evades standard scans. The Australian Cyber Security Centre has guidance on dealing with persistent infections. Alternatively, bring it to us for a professional assessment with enterprise-grade tools.
- Change your passwords from a different device — assume your passwords may have been compromised and change the important ones (email, banking, social media) from a device you know is clean.
When to Call the Professionals
If the infection is severe, if your antivirus won't run, if you've been hit with ransomware, or if you were targeted by a tech support scam (someone called claiming to be Microsoft and got you to install software and give them access), you need professional help.
At PC Madness in Midland, we remove malware using professional tools that go far beyond standard consumer antivirus software. We also check for secondary infections, secure your system, and advise you on what data may have been exposed. We've cleaned thousands of infected machines across Midland and the eastern suburbs since 2003.
For scam victims specifically — even if the computer appears to be running normally after the scammer disconnected — you should get it checked. The tools they install are designed to be invisible. Don't assume everything is fine just because it looks normal.
Think your computer might be infected? Call PC Madness on 08 9250 4554 or drop in to our Midland workshop at 2C Stafford Street. Mon–Fri, 8am–4pm.