There are bots that you can download off the internet that will sit and play for you. There are a million of them so you can pretty much choose on that fits your needs such as playing in tournaments, playing in sitngos etc. It is harder to find bots that play ring games because most are programmed to run based on changing blind levels such as are in tourneys and SnGs. But they are out there.
However, if you get caught using one your account is banned. Any money made on that account with the bot is confiscated by the site and your IP is usually banned as well.
Unfortunatly, it is a growing cost problem for poker sites
because they have to keep up with the new bots coming out that are trying to avoid securities put in place by the sites. The bot makers are pulling in more money selling these bots to build better ones while the sites are tryin to combat them without having to raise rakes and lower bonuses.