what does controlling 51% of the network mean?

[pumawolf]

how would it happen , and what could they do with it? and is there any defense against it if it does happen? thanks guys,gals

[Akka]

It means that you have the ability to completely control the newly found blocks.

Basically you can:

• Orphant all Blocks from other miners
• Completely decide which transaction get confirmed and which not
• Invalid already confirmed transactions that have happened at the time you already had over 50% of the Hashing power (double spend) by orphaning existing blocks

What you can't:

• Steal someone coins
• Make any behaviour that is against the protocol, like for example create new coins out of thin air