[bluedino]

Is DLP even effective?

In my experience it either blocks false positives, or lets sensitive information out with the slightest obfuscation.

[superflyguy]

Try it for yourself - can you exfiltrate anything you like by zipping it up and appending it to a JPEG? I think you'll find you can! (7zip just ignores the image part so you don't have to do anything funky at the other end.)