Trojan:Android/AndroRat is a remote access tool (RAT) embedded into a 'carrier' app (essentially trojanizing). Once the app is installed onto a device, the embedded RAT allows a remote attacker to control the affected device.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
Check for the latest database updates
First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.
Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note You need administrative rights to change the settings.
From the F-Secure Mobile Threat Report Q3 2013:
In July , there were reports of a new toolkit (aka "binders") that simplify the process of inserting malicious code into legitimate Android apps. The binder, named "Androrat APK binder", is used to insert an existing remote access tool (RAT) known as AndroRAT, into a "carrier" app, trojanizing it.
Once the carrier app is installed onto a device, the implanted AndroRAT allows an attacker to remotely control it and among other things, monitor and make calls and messages, activate the camera and microphone, and access stored files.