Anonymous attacks
Richard Stallman considered DDoS offensive as street protests on internet, saying it a mistake to call them hacking (playful cleverness) or cracking (security breaking). Thus RMS supported anonymous attacks on MasterCard as a rightful way of internet public life, protesting the embargo on WikiLeaks and Julian Assange.
Functioning in a leaderless activism under anonymity, this has become an invincible hacktivist setup that impersonally works, involving activists all over the world.