Mail filter evasion

Corporate mail filters don’t tend to respect the fact that you’re not a moron. Sometimes you need to get that HTML report out but the zip file gets rejected because it contains JavaScript, other times you need to send out a patched executable to a client or colleague but they have no way of downloading or receiving it.

To address this problem I created a couple of little tools. File2BMP is a tool for Windows, written in VB6, which will convert a file into a bitmap image and back again. It XORs the entire file so your mail filter won’t detect it too. Just drag and drop the file on to the window, click the “go” button and you get something like this:

As usual, you can grab a Windows binary and the source code.

At at least one government contract I worked at, security was so tight that you couldn’t download an exe from the web or even stick this tool on a CD, floppy or flash drive, so I made another solution. FileStore.mdb is a Microsoft Access database which can archive into and extract files from itself, you just give it the path to the file, click the button and send the database. If it does get rejected you can just set a password to encrypt the database before transit.

It’s a shame that Microsoft Access isn’t part of Office or it would be a great tool for bypassing security. It could be adapted to work for Microsoft Word, but VBA macros are usually seen as suspect by most email blockers anyway.