Curious -- so looking at just Alt-Coins -- and not LTC -- what would you consider to be "rival pools?"
I've been mining Altcoins for about 4 months now on one particular and popular pool -- and this is the first time I've seen the attacks happen.
this time is definitely over... I remember at maxcoin launch that the 2 pools (1gh and ypool) were getting ddos in turn, now nobody really care about ddos'ing a pool of the coin.
Also most pool have some protection implemented already.
And there isn't much coin worth ddosing, it works only for coin successful at launch (meaning small number of pools) and I haven't anything lately which be good enough to worth the effort.
At the moment coins which are popular (and worth ddosing) have too many pool and ddosing wouldn't give any advantage, and those which have too little pools (good candidate for ddosing) are in most case shitcoins nobody want. so no more ddos...
(and big and serious pool have all protections against ddos attack...)