What (exactly) is required for a 51% attack?

[shmadz]

I've read a lot of speculation about the 51% attack but a recent bit of FUD made me reconsider.

For your consideration: http://www.youtube.com/watch?v=h2u3BNiANVA   skip to around 3:40 for the juicy part.

Basically he is saying that any entity with roughly 35% of the network could reasonably expect to be able to perform a 51% attack within 7-10 days...

I thought this was nuts. no chance. so I went and checked the last 100 transactions at btc guild and boom, 6 blocks in a row (233302-233307 check it yourself)

since you can currently spend bitcoin after 6 confirmations, does that mean that creating the last 6 blocks allows you to double-spend?

what exactly is required to perform a "51%" attack?

[Rodyland]

Blocks in a row are irrelevant. To double spend  you need to rewrite history . Which means mining ahead of the network, then spending, then releasing your mined blocks.

I am sure there is stuff about this on the wiki .                 

[BitcoinAshley]

This does not belong in "Speculation." Please move it to a more appropriate section of the forum.  Note that OPs can move their own topics.

Also, I'd recommend reading up on 51% attack in the wiki or the technical section of the forum.