It would depend on what operating system you're running on your device. If you have 4.3.1 or 4.3.2, then the jailbreak is redsn0w. If you have earlier operating systems you might have to use greenpois0n, limera1n, blackra1n, or the pwnge tool. Hackulous is one of the repositories you can add to Cydia that has malware protection tool. So your not completely vulnerable.
You can check the following site for the right program. Jailbreaking your iPhone is generally not recommended because it puts your device at risk of being attacked by viruses and other harmful programs. It also voids the manufacturer's warranty.