Which addon is responsible for this? * .dat

[musicus]

In the Attachments folder, most addons are ending with * .dat
Which addon is responsible for this?
I know the extension * .321 from the plugin "Attachment Extension for SMF 2.0.x" comes, but the upper is a mystery to me.

[Sir Osis of Liver]

That looks like a file type, not an extension.  What are you using to view it?