I call bull on this "DDoS" excuse. EA/DICE claimed the same thing with BF3 earlier this year, despite the fact that chronic, unrepairable server crashes have been a problem for that game since late 2012. They haven't provided a shred of evidence to back up their claim of outside-party shenanigans.
I'm not alone in suspecting that Battlefield's crappy network code is ultimately to blame for the server crashes, especially when considering how many other factors they've tried to bring into blame -- PunkBuster, hardware conflicts, Origin/Battlelog interference, busted registry entries, improper game installation, outdated .dat files, blah blah fucking blah.
It's a smokescreen. DICE are incapable of fixing an ongoing problem, so they're making shit up now and hoping their customers will eat it without thinking.