3DES has become fairly weak, and it seems like most cryptographers wouldn't recommend it - especially if you are trying to defeat the NSA - originally it had a 168 bits, but with known attacks, it's reckoned to have around 80 bits of security left, which given DES was considered insecure with 56 bits makes it sound iffy at best.
Well...there's "insecure"...and then there's really insecure.
DES (and by extension 3DES) isn't, per se, "insecure" at 56-bits except that technology has progressed from the mid-1970s such that an exhaustive search of the keyspace (e.g. brute force) is now practical in reasonable time. DES is resistant to differential analysis and even more modern techniques that could seriously reduce DES security are theoretical exercises at best (like those requiring terabytes of known plain-text to derive a key, or those only applicable to reduced-round implementations).
Yes, I'm aware that to a cryptographer, "theoretical attack possible" == "OMFG insecure cipher", and that attitude is a good thing. If DES was an AES candidate we'd never pick it. But from a practical standpoint, baring implementation mistakes or operational missteps, no one using known 2015 tech and technique is cracking 3DES before the heat death of the universe (or at least before we're long turned to dust).
That said, can you provide a reference to a practical (that is, not the linear cryptanalysis stuff from Davies) attack which reduces 3DES to 80-bits of effective security? If it's there, I missed it, and would invalidate what I've said.
