09 July 2005

Very interesting pair of trojans
SymbOS/Onehop.A and SymbOS/Bootton.A

Bootton in action

NAME: Bootton.A
ALIAS: SymbOS/Bootton.A

Bootton.A is a SIS file trojan that is sent over bluetooth by SymbOS/Onehop.A trojan.

In its structure Bootton.A is quite similar to Skulls family trojans. With the exception that instead of replacing system files with corrupted binaries,the Bootton.A uses application that causes device to reboot.

Thus if a device is infected with Bootton.A, pressing menu button or any system application button the device immediately reboots.

Bootton.A disables most of critical system functions and third party file managers, so that even if the device wouldn't immediately reboot it is still unusable before it is disinfected.

In addition of disabling applications on the phone, the Bootton.A also installs modified Cabir that SymbOS/Onehop.A uses to distribute Bootton.A. But this file does not get executed automatically, and even if started by user is unable to send anything as the file it is trying to send does not exist on the system.

Like Skulls.A the Bootton.A replaces the application icons with it's own icon, this time the icon is a heart icon with the text "I-Love-U"

Disinfection with two Series 60 phones

Download F-Skulls tool from ftp://ftp.f-secure.com/anti-virus/tools/f-skulls.zip or directly with phone http://www.europe.f-secure.com/tools/f-skulls.sis

1. Install F-Skulls.sis into infected phones memory card with a clean phone
2. Put the memory card with F-Skulls into infected phone
3. Start up the infected phone, the application menu should work now
4. Press menu button until you get Symbian process menu, look for any applications with heart icon. Kill the application processes with 'C' button.
5. Go to application manager and uninstall the SIS file in which you installed the Bootton.A
6. Download F-Secure Mobile Anti-Virus from http://phoneav.com and activate the Anti-Virus
7. Scan the phone and remove any remaining components of Bootton.A
8. Remove the F-Skulls with application manager as the phone is now cleaned

Installation to system Bootton.A is a SIS file that installs small component that resets the device if executed, this component is installed into locations where it replaces system and third party applications.

Spreading in ILoveU.sis

Payload Replaces built in and third party applications with component that causes device to reboot when executed.

Generic detection that detects Bootton.A was published for F-Secure Mobile Anti-Virus on November 19th, 2004 in database build number 11.

Exact detection for Bootton.A was published for F-Secure Mobile Anti-Virus on July 8th, 2005 in database build number 44.

F-Secure Corporation