Some “.js” files in e-mail are now blocked
For a long time, our mail system has blocked many malicious filename extensions.
Recently, we’ve seen an increase in “.js” files that spread various forms of malware. These change their “patterns” often enough that they’re sometimes not detected by virus scanners.
Legitimate “.js” files are common in e-mail, so it’s impossible to block them outright. (They’re often sent as part of a package of website files — for example, a zipped copy of the WordPress files contains them.)
However, legitimate “.js” files almost always occur as part of an archive containing other files. They almost never occur alone, as they do in the malware versions.
Because of that, our e-mail system now blocks “.zip” files that contain only a single “.js” file, on the assumption that they’re almost certainly malicious.
We don’t expect this to cause any problems, but as always, don’t hesitate to contact us if you have any questions or trouble.