Yes, Blowfish is an encryption cipher, there are various DLLs which allow it's use in mIRC.
For the records there's absolutely nothing about encryption or decryption something that makes it an 'excellent way of having things go really wrong with your computer'. If you're referring to the $decode() 'exploit', then you might want to take note of a couple of things:
a) $decode() doesn't use encryption/decryption.
b) The exploit is an exploitation of people's stupidity, not of decoding information. If people choose to execute code without being able to see or understand what it does that's their own fault.
