Today's smartphones are powerful computers that allow us to perform tasks that only a generation ago would have been considered science fiction. The devices also often contain a tremendous amount of confidential information, including the contents of our text and email communications, as well as access to various accounts via pre-logged-in apps. It is imperative, therefore, to keep the devices safe from hackers, and to take immediate corrective action if one's phone is breached. But how can you tell if your smartphone has been compromised? Below are some symptoms to look out for.
Please keep in mind, however, that none of the clues that I discuss in this article exists in a vacuum, or is, on its own, in any way absolute. There are reasons other than a breach that may cause devices to act abnormally. However, if your device suddenly starts exhibiting multiple questionable behaviors, or the relevant issues develop shortly after you clicked some link, downloaded some app from a third-party market, opened some attachment, or otherwise did something that you now question, you may want to take corrective action, as discussed below:
Your smartphone or tablet seems slower than before
Malware running in the background can impact the performance of legitimate apps on a device, and malware transmissions can slow down a device's network connection. It is important to realize, however, that updates to a device's operating system can sometimes also cause a device to suffer from decreased performance, so don't panic if you just updated your operating system and performance now seems degraded. Likewise, if you fill up the memory on your device or install many processor and bandwidth intensive apps, performance can also drop.
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.
Your device's battery drains more quickly than before
Extra code running in the background (for example, malware that is constantly monitoring and capturing user activity and relaying it to third parties) uses battery power.
Your device is hotter than before
For the same reason, it may also run physically "hotter" than before.
Websites appear somewhat different than before
If someone has installed malware that is "proxying" on your device--that is, sitting between your browser and the internet and relaying the communications between them (while reading all of the contents of the communications and, perhaps, inserting various instructions of its own)--it might affect how some sites display.
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 cell-phone bill shows unexpected charges
Criminals can exploit an infected device to make expensive overseas phone calls on behalf of a remote party proxying through your device, can send SMS messages to international numbers, or ring up charges in other ways.
"Pop-ups" appear on your device--and they never appeared before
Just like on computers, some mobile-device malware produces pop-up windows asking the user to perform various actions. If you are seeing pop-ups, beware.
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.
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.
You are experiencing unusual service disruptions
If you experience calls being dropped, the inability to make calls at times when you appear to have good signal strength, or strange noises occurring during your phone conversations, something may be amiss. Normally, these problems are indicative of technical issues unrelated to a breach, but that is not always the case. So, if you noticed these symptoms shortly after you took some action that you now regret, you may wish to consider whether you need to take corrective action.
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.