Saturday, November 04, 2006

Mobile Telephone Evidence

Code and Data go hand in hand

Examiners are familiar with the fact that from time to time found appended to SMS text messages there appears unintelligible code that cannot be read in context with the user's message itself. Such code as @@@ or /./@@ and so on may raise the notion that the SIM reader has not decoded the message correctly. On the contrary, the SIM reader is most likely to have done its job. The assignment of code being added to the data is so that the mobile telephone knows what to do with a message next time it reads it. The cause behind this is fairly straightforward. Phase 2+ handsets (GSM Release 98 onwards) adopted UCS2 (Universal Character Set 2) that allowed highlights to be added to or with data. For instance, italics or colours and so on. Most GSM SIMs' are programmed with GSM Default Alphabet and not UCS2. To corroborate finding code with data, following a SIM read, may require viewing the message through the handset.

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