Can players use hacking software to gain an advantage or hack into the actual poker servers?
To answer the first question, I can only speculate, but my answer is no. A competant programmer would know that in order to make the game as secure as possible, the client (software on the player's computer) should only be sent information about it's own cards. Your computer is thus, on a "need to know basis". The only time you need to know your opponents card is during showdown, so only then is your computer sent that information. If this programming practice is carried out, then you should never be able to know your opponent's card ahead of time. So no, don't even bother looking on the Internet for PartyPoker cheats or whatever.
What is a viable attack point for hackers however, are the actual poker servers. Since this FAQ is about poker and not hacking, I'm not going to get in-depth about the methods that hackers use, but the idea behind most attacks is to find an exploit or weakness in the software and gain administrative privileges (root). Given that most of the software in use by the online poker sites are proprietary, it does add a layer of challenge for potential hackers. This in itself means that the chances of being hacked by any amateur or mediocre hacker very slim (if the system is locked down properly, that is). In the event that the site is facing a very intelligent and determined hacker, it's the hope of the site that their software is secure and well written to stop any break-ins.
My honest opinion is that no site is hack proof, but there has been a lot of money invested in these sites, so they are probably very secure. In any event though, your money will probably never be at risk from professional hackers who target the poker servers.
NEXT: What are the 'pattern mappers' on eBay and do they really work?
PREVIOUS: What is "chip dumping"?
