My computer is acting up: a virus or just a slow PC?

"My computer is acting up." It is one of the most common questions our helpdesk gets, and the answer is far from always a virus. Sometimes a PC is simply old or overloaded, sometimes something really is wrong. The trouble is that the symptoms look alike, and that needless panic can be as harmful as too little action. Below we help you see the difference.

When it is probably just slowness

A PC that gradually gets slower, without any other strange behaviour, usually points to plain wear or overload. Annoying, but not dangerous. Typical causes:

• Too little memory (RAM) for what you do daily, especially with many browser windows open.
• An almost full hard drive, leaving Windows no room to work smoothly.
• Too many programs that start automatically and keep running in the background.
• Ageing hardware, for example a classic hard drive where a faster SSD would do wonders.

The telltale sign: the slowness is always there, fairly predictable, and does not suddenly change from one day to the next. In that case a virus is unlikely.

Signals that point more to malware

Malware often gives itself away through behaviour you did not set in motion. Watch for these signs, especially when several appear at once:

• Pop-ups and adverts that appear, even when you have no browser open.
• The PC suddenly became much slower, from one day to the next, for no clear reason.
• Your browser opens a different home page or search engine than the one you set.
• Unknown browser extensions or programs you never installed yourself.
• Unknown processes claiming a lot of computing power, visible in Task Manager.
• Friends or colleagues receive messages from you that you never sent.

A pop-up demanding that you call a number or pay immediately is almost always a scam. Do not call that number and do not pay anything.

Practical first steps

If you suspect malware, acting calmly and methodically matters more than acting fast. In this order:

1. First save your important files, ideally to a location that is then disconnected.
2. Cut the internet connection to limit further damage and spread.
3. Run a full scan with the built-in Windows security or your antivirus.
4. Remove browser extensions and programs you do not recognise.
5. Change important passwords, but only after the PC is clean again, not before.

If it is only about slowness, the following often already helps: limiting startup programs, freeing up disk space, and checking whether a memory upgrade or SSD makes sense.

When you are better off getting help

Some things are better not tackled alone. Get help if a scan finds something but cannot fully clean it, if the problem returns after a cleanup, or if it concerns a device with company data and access to your email or accounting. In those cases you want to be sure nothing is left behind, and that you do not pass an infection on to colleagues or clients.