Preface: We have no idea whether the Chechen brothers who are alleged to have carried out the Boston terrorist attacks are guilty or not. If half of what the FBI claims is true, then they are. But it is also important to be aware of history.
In 1999, the Russian KGB allegedly conducted a wave of bombings in Russia in order to justify war against Chechnya and put Vladimir Putin into power (see also this short essay and this report).
The 1999 bombings were apparently a false flag attack wrongfully blamed on Chechen terrorists.