Q: I have a jealous husband. On my iPhone 3G I have been texting with an old high school boyfriend – flirting maybe, but nothing more. I’ve read that all my texts are stored on my SIM card. Is there some way to permanently delete text messages? If not, how many are saved?

– Anonymous

A: Actually, in the case of the iPhone SMS messages are not stored on the SIM card, but rather in the iPhone’s own memory. This is actually the case with most smartphones, since these devices have more than sufficient internal memory to store SMS and MMS messages and therefore do not need to rely on the SIM card. Many older “dumb” phones relied on the SIM card for SMS storage simply because they did not have any internal memory in which to store them. Even in these cases, the SIM card could generally only store the most recent 20-30 SMS messages.

With the iPhone, deleting SMS messages directly on the device will effectively remove them permanently from any normal means of access. However, SMS messages are also backed up to iTunes as part of your normal iPhone backup process. iTunes itself normally only keeps the most recent backup of your iPhone, but if you’re backing up your computer itself, then those backups may contain older copies of the iPhone backups that were created by iTunes at the time.

Lastly, there is no guarantee that any data normally deleted on the iPhone itself cannot be recovered through actual forensic procedures. The only reasonable assurance against this would be to wipe your iPhone completely by using the “Erase all Data” option found in the “General” section under the “Settings” app. This option basically overwrites all information on the iPhone’s internal memory and may take a couple of hours to run. Even in this case, however, your iTunes backup may still include deleted SMS messages and other information hidden within the various database files that the iPhone maintains, and restoring this backup would put that information back onto your iPhone. In any case, however, this information would only be accessible by somebody with technology expertise who was specifically looking for it.