What is something that generally wouldn't help with avoiding Trojan infections on Symbian-based devices?

What is something that generally wouldn't help with avoiding Trojan infections on Symbian-based devices?

• Upgrade your device every 12 months
• Use mobile security software
• Keep firmware and OS versions up to date.
• Install only Symbian-signed or trusted programs 

EXPLANATION

A Trojan is a program that looks genuine but has a disruptive agenda. The motive behind designing a Trojan is to get access to data inside a person’s computer.
It gives access to your most sensitive data that may include credit card information. This is done by creating a backdoor. You can protect yourself against Trojans by downloading software and programs that come from known and verified sources, and not obtained by a random search on the Internet.