It all depends what you do with the jailbreak. Some people go wild with downloading all sorts of customizing apps, and some try apps that pirate, bypass or allow free entrance into paid subscriptions. Those people usually get viruses or popups on their phones. If you stick with trusted sources it should operate as well as any other phone. I've jailbroken several iPhone generations and have never had any security issues. Just do your research until the next jailbreak is available and you'll be fine.