Introducing tools to turn mail attachments into risk-free copies and examine them carefully before opening them.
Don’t trust email attachments. But no matter how carefully you check your inbox for phishing attacks and how suspicious you are of e-mails: sooner or later an attachment will appear whose intentions are unclear and which you cannot ignore because the content promises to be important.
So you need to somehow mitigate the risk posed by the attachment before you open it. You have a number of options for doing this; Let’s start with the simplest: Check whether an online virus scanner like virustotal.com recognizes the attachment. However, not by simply uploading the file there, otherwise you will all too easily have a data protection problem to deal with. Instead, compute a unique hash of the file locally and enter that into VirusTotal’s search. No data can be reconstructed from the hash, but if it is a known file, this gives you an assessment of the service. Virus documents are usually widely distributed, so with a bit of luck there will already be a report on an infected file.
The fastest way to calculate a suitable hash is on the command line, under Windows with the PowerShell command Get-FileHash DATEIunder Linux per sha256sum DATEI and on macOS with shasum -a 256 DATEI. But there are also various tools with a graphical interface that can calculate hashes; VirusTotal finds hash values ​​of the methods MD5, SHA-1 and SHA-256. (It’s best to use the last one, it’s considered perfectly safe.)