Arbitrage involves exploiting differing opinions of bookmakers to try and guarantee yourself a no lose bet.

A classic easy to visualise example might be a cricket match between Australia and England.

With patriotic cash piling onto England uk bookies might offer 11/10 about Australia.

On the other side of the world however the aussies are betting the opposite way  and due to weight of money the Australian bookmakers offer 11/10 about England.

Put £100 on both sides at 11/10 and you are guaranteed a profit no matter which team wins.

Every day there are many many such opportunities available.
It takes work to find them manually however.

Software can be used however to do the tedious job of scouring markets and doing the sums.

A well know example of such software is Rebel Betting

A new kid on the block however is now offering a potentially better idea.
That being that it will not only seek out arbitrage opportunities.
It will do the extra step of logging into bookmakers and placing appropriate bets for you !

Bullet Proof Bets are the ones offering such software.

I will have to hold my hands up and say I have yet to test it thoroughly.
I am however drawn by the principle about what it offers.
That being making cash from betting with little investment of time.

It comes with quite a bit of hype which I normally find off putting but it might be worth  you taking a closer look if you are also drawn by its key design feature of trying to be an automated cash earning machine.

Rebel Betting is also worth a look if you just want to the computer to find arbs and do not trust a computer to take hold of your bankroll.
It is older and more tested and checks a much wider range of bookmakers.