In June this year I experienced what I've found to be called the "Selfmite" worm on my Nexus 5 smartphone.
On 24.06 and 29.06 it sent the message "Dear [contact name], Look The Self-time, http://goo.gl/[...]" to 13 of my contacts, chosen in what seems to be a random order.
Once I realised this had happened, I looked the issue up on Google through the phrase used in the message and found that this worm should actually install itself as an app called "The self-timer" that you should be able to uninstall, but I could not find this after looking through all of the installed apps listed in the settings page.
At the time I had enabled the security option within Android that allows the installastion of apps from unknown sources and I realized my mistake then, though I do not know how the worm actually reached my phone since I had never clicked any dodgy links in messages or the internet.
After this I disabled the installation of apps outside of the Play Store, and installed the avast! Mobile Security app for whatever help it may be in the future.
It wasn't until this Saturday, on 23.08, that the messages were sent again to the same contacts. I had not touched any security settings, nor had I accessed any sketchy sites, and once more I have found no unusual app to have installed itself.
My question now is, does anyone know of a way to prevent another occurence of this without actually wiping my phone clean? Though I wouldn't know if this would even help as I don't understand how the worm exists in the phone in the first place.
Would activating Avast's firewall within their app be of use? Rather, I'm asking if going through the hassle of rooting the phone is worth the trouble.
Thank you in advance to anyone who has advice or opinions to offer.