5 subtle signs your laptop or phone has been hacked

Yahoo

22-05-2025

Cyberattacks have been making headlines in recent weeks, with Marks & Spencer revealing a major hack will continue to impact its operations until July.
Hackers targeted the IT help desk at the company over the Easter weekend, convincing workers to allow them to reset passwords to gain access to their networks, before unleashing malicious software (malware). The attack, which will cost the retailer an estimated £300m, left M&S with empty shelves as well as halting orders on its website, which has still not seen resolved.
Customer personal data, which could have included names, email addresses, postal addresses and dates of birth, was also taken by hackers in the attack.
The Co-op was another high-profile victim in recent weeks, but cyber attackers do not just limit themselves to major brands.They can - and do - gain access to home computers, often via phishing attacks from emails, or via malware downloaded from compromised websites or via dodgy software.
Cyber attackers will mostly attempt to gain control of a computer or mobile device in order to steal, for example by accessing bank accounts or taking out loans in a person's name.
But what are the common signs that your computer or smartphone has been compromised? Some are obvious: a ransomware attack (similar to the one on M&S) will announce itself with a window demanding a ransom, usually payable in cryptocurrency.
But other signs are much more subtle, experts have told Yahoo News.
If an attacker is in control of your accounts, they may delete some of your emails or have them forwarded to another address, says Javvad Malik, lead security awareness advocate at security firm KnowBe4.
"One thing to look out for is the unexplained disappearance of emails, particularly those related to financial transactions," Malik says. "This could signify an attacker's attempt to conceal unauthorised activities by intercepting and deleting confirmation messages.
Attackers will also commonly divert emails to an address they control, so that the user cannot see them, Malik says.
Visit your email settings to check there are no 'rules' which automatically forward certain emails to another address, Malik advises.
Other related signs are that your passwords change, you're locked out of accounts, or suddenly logged out of accounts.
If your device starts displaying unusual pop-up windows, either containing advertising or other messages, it's a good sign you may be running unauthorised software or malware, Malik warns.
Another warning sign is that your browser redirects you to pages you didn't ask it to.
Both of these are classic signs of software that is either serving unwanted adverts or trying to defraud consumers.
On smartphones, the signs are more subtle. "For mobile devices, unexpected increase in data usage could indicate some unwanted application activity taking place.," says Malik.
On a computer, the first thing many malware infections do is to disable antivirus software, warns Brian Higgins, security specialist at Comparitech.
'It's not uncommon for malware to deactivate these measures as part of their exploit payload so it's a good indication that you need to take action," Higgins explains.
Malware does this in order to prevent detection, and this can offer a warning sign that your computer has been compromised.
Higgins advises: 'Carry out random but frequent checks on any products you are running to check their status.
Malicious software often prevents your computer operating properly, and sometimes stops you shutting it down or restarting (this allows the malware to keep running).
Frequent error messages can also be a sign that something is wrong, says Chris Hauk, consumer privacy advocate at Pixel Privacy.
'Keep an eye out for unusual activity on your computer or device. If your computer or mobile device begins crashing or you're seeing repeated error messages, your device could have malware on it," he warns.
'While malware-as-a-service has made it easy for even rookie hackers to infect your device, not all malware is well-written, which could result in crashes and error messages."
On mobile devices, a sign that something is wrong can be that battery life suddenly changes for the worse, Hauk warns.
"On mobile devices, keep an eye on your device's battery life. Poorly written malware can result in extreme battery drain on your device. Even well-written apps can put a strain on your device's battery," he says.