Your device may have a virus if:
1. Apps start crashing often
2. You suddenly start receiving lots of pop-ups
3. You notice unwanted apps
4. Device is hot even when idle
5. Battery starts wearing down faster
6. Data usage is suddenly up (if not on unlimited
plan, you may notice extra charges on bill)
Go into settings and back up everything to ICloud. Then in settings go to General and Reset. Choose "Erase all content and settings." Once restored to factory condition, restart device, sign into ICloud to restore your info. If this doesn't work, go to the Apple Genius Bar at your local Apple store.
Go into Settings and find Apps or Application Manager. Find suspicious apps and clear cache and data on them and then uninstall. Some malicious apps may require you to go into Security Settings and uncheck Administrator Permission first. Then go back to Apps and uninstall. Restart device.
1. Don't jailbreak your device2. Don't install apps from unknown sources. Only
get your apps at the Apple Store or Google
3. Don't tap on suspicious links. Be vigilant. If
something seems strange, don't tap on it.