There is a unique feature in Symbian OS v9.4, Series 60 rel. 5 where you can lock your phone remotely by sending an SMS.
Reset Default lock code:
1) Go to Menu -> Settings -> Phone -> Phone mgmt. -> Security -> Phone and SIM card.
2) Click on “Lock Code”. you will be asked to give existing lock code. This code depends on the mobile phone model and the right code will be specified in the phone’s user manual. for example, for 5800XM, the phone lock code will be 12345 by default.
Remote Phone Lock:
From the same menu, select “Remote Phone Locking”.
You will be asked to enter new “Remote Locking Message”. This will be the message that you have to send in SMS when you want to lock the phone.
eg: lock from thief
Reenter the same message for verification.
If both the messages are identical, you will be asked to enter the lock code.
Use the phone’s lock code and if everything is enetered properly, you will get the message “Code Accepted”.
How to Lock:
In case you lost your phone and you want to lock your phone, SIM and memory card, you just send an SMS to your phone with the subject being the “Remote locking message” like “lock from thief”.
Once the SMS reaches the phone, SIM/phone/memory card will be locked and the phone user need to enter the right lock code to unlock the phone.