Slowing down of the smartphone, frequent overheating, and uncontrollable changes to GPS, Wi-Fi, or mobile data settings can be signs that the device is infected with malicious software, Ruslan Permyakov, Deputy Director of the NTI Competence Center Trusted Interaction Technologies, told RIA Novosti.

"Signs of infection: ... If your phone has become unusually slow, discharges quickly, or overheats, this could be a sign of malicious activity ... Uncontrolled changes to device settings, such as GPS, Wi-Fi, or mobile data, can also indicate the presence of malware," Permyakov said.

He added that malware running in the background can also be indicated by a sudden increase in the user's mobile phone bill without changes in network usage habits or the appearance of new apps on the device that the user did not install.

The expert reminded that it is important to regularly update the operating system and apps, use antivirus software, and download apps only from official sources, such as Google Play or the App Store.

He also recommended being cautious when using Wi-Fi, using virtual private networks (VPNs) to protect data when using public networks, and regularly backing up data.