I'm discovering alt-coins.

Now, I'm on piratecoin.

{
    "blocks" : 34167,
    "currentblocksize" : 1225,
    "currentblocktx" : 1,
    "difficulty" : 0.14348426,
    "errors" : "",
    "generate" : true,
    "genproclimit" : -1,
    "hashespersec" : 355,
    "networkhashps" : 11127177,
    "pooledtx" : 1,
    "testnet" : false
}

There is somehow calculated networkhashps, seems it is aproximation from difficulty, it is 11,127,177, ~ 11mh/s. I'm count on my own, 350h/s, however, cgminer show me 180Kh/s. Probably it doesn't counts in getmininginfo or recalculated somehow. Anybody?

I've seen persons with much greater speed, its called mining rig. 20-30 may be 100 GPU in a bunch.

What if such huge miner connect to such young alt-coin network, download whole of current blockchain, and start mining off-line. After 5 hours he come back to network, his blockchain will be with bigger difficulty.

Can he attack network in such way?