Your device is attempting to access “bad” sites
If you use your device on a network that blocks access to known problematic sites and networks (many businesses have such technology on both their corporate and bring-your-own-device (BYOD) networks) and you find out that it was trying to access such sites without your knowledge, your device may be infected.
Your device is sending or receiving strange text messages
If your friends or colleagues report receiving messages that you didn’t send, something may be amiss (this is true for emails as well). Likewise, if you see strange text messages coming in, they may be related to a breach.
New apps are installed on your device–and you didn’t install them
While your device manufacturer or service provider may legitimately install apps from time to time due to updates, if new apps are suddenly appearing you want to be sure they are kosher. Do a Google search on the apps and see what reliable tech sites say about them. As I discussed in an article last week, vulnerabilities in operating systems may let Android or iOS malware escalate privileges and thereby gain the ability to circumvent security features–allowing it to potentially steal your data, record your calls and text messages, hijack your social-media and online banking sessions, and wreak all sorts of havoc.
Some apps stop working properly
If apps that used to work properly suddenly stop working, that may also be a sign of proxying or other malware interfering with the apps’ functionality.
You notice an increased use of data or text messaging (SMS)
If you monitor your data or SMS usage and see greater use than expected, especially if that increase begins right after some “suspicious event,” that may be a sign that malware is transmitting data from your device to other parties. You can even check your data usage per app–if one of them looks like it is using way too much data for the functionality that it provides, something may be amiss. If you installed the app from a third party appstore you can try deleting the app and reinstalling it from a more trusted source–but if there is malware on your device, doing so may not always fix the problem.
Your email from the device is getting blocked by spam filters
If email sent from your device is suddenly getting blocked by spam filters it could be a sign that your email configuration has been changed and email is now being relayed via some unauthorized server that is allowing a nefarious party to read your messages.
Data breaches and/or leaks
Of course, if you have experienced some data leak you should always check to determine the source of the problem–and the process of checking obviously includes examining your smartphone.
So what should you do if you suspect your device was hacked?
If you suspect that your phone is infected, run mobile anti-malware software (preferably run more than one vendor’s offering) and remove any apps that you don’t recognize. If possible, wipe the device, restore factory settings, and reinstall apps from trusted appstores. Obviously, use internet security software on your device going forward. If you are concerned that the device has been rooted by malware, show it to a professional.