The golden rule of digital hygiene is to never open unexpected attachments, even from friends. If you have already downloaded a suspicious RAR file, do not extract it. Instead, experts from the Purism community and other security forums recommend uploading the file to a multi-engine scanner like VirusTotal to check for hidden threats before touching it.

Because you trust the sender, you download and open the RAR.

You receive a message from a friend saying, "haha, look at this!" with the attached file.

It may attempt to shut down task managers or antivirus software to hide its presence.

If you believe your system is infected, run a full system scan with a reputable antivirus immediately.