(: these aren't the droids you're looking for. taking down the internet (or specific pockets of it) via BGP is not a question of method, it's a question of access. BGP hijacking can be easily done by computer science grad students... state actors would not need to test a "cyberweapon" that messes with BGP routes.

edit: the point being, how to do it is not an issue. they're not in the position to do it. ...but if you were thinking of censorship or outright disruptive terrorism via BGP, you'd be looking for infiltrating network operator jobs, not developing an attack. the attacks themselves are trivial, well-documented, and often happen accidentally.

edit2: "sorry we broke the internet" http://seclists.org/nanog/1997/Apr/444

Internet Truth #33, as told by Mr. V: "If the interstate highway system ran the way we run internet, then in the middle of the rush hour a giant sinkhole would open in the middle of i495, swallow twenty thousand cars without a trace, a sinkhole would close and we would still call it a good day"

"A while" being "two decades"