He's reading your texts and emails. She's monitoring your calls. You're afraid he's tracking your phone's location when you travel, or using spyware to read every word you type into your computer.
What can you do if you think your husband, wife, partner, lover, boyfriend, girlfriend, ex or anyone else is inappropriately monitoring you?
According to a 2009 report by the U.S. Department of Justice, 1 in 6 women and 1 in 19 men experience stalking at some point in their lives. Sixty-six percent of these women were stalked by a current or former intimate partner. And 31 percent of those stalked by a current or former partner were sexually assaulted by that person.
Not all stalkers are abusers, but stalking sometimes does turn into abuse. The following tech tips may be able to help regain control of your digital life.
Editors' Note: This article includes advice on how you can determine whether someone is surveilling you without your knowledge. It does not constitute legal advice. If you feel you are in danger, please contact the proper authorities immediately.
Adjust your social-media and browser settings
If you're afraid someone is spying on you, you've probably already stopped posting pictures to Facebook or checking in on Foursquare. That's good. Next, remove location data from your Facebook posts and tweets, including any attached photographs, and recheck the privacy settings for all your social-media accounts. (Here's more on how to lock down your Facebook privacy and security settings.)
If you're worried about being stalked by someone you live with, and that person has access to your computer, he or she will be able to see your browser history. You don't want your stalker learning that you've searched for ways to avoid him or her, as that could trigger a confrontation.
Fortunately, editing or erasing your browsing history is easy. Go into your browser's settings and find the option called History. It will bring up a list of all Web pages recently viewed. Find and delete any records you don't want the person you suspect of stalking you to see. (Note that deleting your entire browsing history might raise suspicions.) Then close the browser.
The next time you want to secretly look at a Web page, you can use your browser's Incognito mode (as it's called in Chrome), also called Private Browsing in Firefox and Safari, and InPrivate Browsing in Internet Explorer. In this mode, the browser won't save your browsing history.
If your stalker has installed monitoring hardware or software onto your computer, erasing browser history might not help. A keylogger, for example, records everything typed into a computer, including something like "my husband is spying on me." Keyloggers also record passwords, emails, instant messages and anything else you've typed.
Discover the pattern of surveillance
You might consider installing tiny spy cameras in your home, so you can verify whether someone is entering your home or touching your computers or devices. That's the recommendation of Bob Leonard, a former New York City police officer and the proprietor of the Manhattan-based Spy Store. Leonard sells home-surveillance devices such as cameras and voice recorders, and also offers consultations.
Before taking this step, you may need to check on the laws of your states to see if cameras in your own home are illegal.
Cindy Southworth of the National Network to End Domestic Violence (NNEDV) in Washington, D.C., has different advice. If you believe that your partner is inappropriately surveilling you, she urges you to "trust your instincts."
If you have any doubt that someone is following you, Southworth said, try to conduct little tests to figure out how he or she is doing so. Is there a tracker in your car or on your phone? Is someone reading your emails or texts? Experiment with different methods, and eventually you may be able to figure out how that person is tracking you.
Southworth also advises her clients not to try to out-snoop their snoops. For one thing, it's more difficult to win a court case if you were engaging in the same behavior as your stalker, even if your stalker started first.
In some cases, Southworth warns, stalking may lead to assault or domestic abuse. When that is a risk, if your stalker discovers you've been trying to spy on him or her in return, it may trigger a violent confrontation.
Factory-reset or upgrade your phone to eliminate spyware
Several companies sell monitoring apps intended for use by parents, who can secretly place the devices on their children's smartphones to keep track of their whereabouts and communications. However, there's little to prevent jealous spouses from using such apps on each other, and there's often no way to tell whether one is installed on your phone.
There's a simple way to get rid of most such apps, though: Restore your phone to its factory settings, which should wipe all but the sneakiest spyware from your phone. Make sure you back up your device to the cloud or a computer (but encrypt that computer backup) before factory-resetting the device, then hand-select each and every app before allowing it back on the refreshed device.
Doing this will also wipe the contacts and photos from your phone, but if you backed them up first, it should only take about an hour to get your phone in much the same shape as it was before.
If you'd rather not wipe your phone, sometimes upgrading the device's operating system will be enough to eliminate spyware that's compatible only with earlier versions. However, that's assuming there's a later version of the OS to upgrade to, and that the spyware won't work with the newer system.
Go to a safe computer
If you have any doubts about your home computer or smartphone, don't trust those devices. But you may need a computer or phone to ask for help or to escape a bad situation.
In that case, get to a computer or device that your potential stalker can't touch, such as a library computer or a friend's smartphone. Set up a new, Web-based email account from one of these safe devices, and never check the account from your regular computer or phone.
Never be without a phone
If you suspect you're being tracked via your phone, you'll need to ditch it if you plan to escape. But first, Southworth said, go to a local electronics store and pick up a cheap disposable cellphone. You never want to be without a way to call for help, even if you throw away each phone after just a few hours.
Change your contact info and passwords, and wipe your devices
If you've already fled a bad situation, you'll need to lay low and set up an entirely new set of contact information Changing your phone number, email addresses, online accounts and passwords can be a serious hassle, but if you can do it, you should.
When changing passwords, you may also need to change your security questions. A stalker who knows you intimately, even one who's a stranger to you, is very likely to know personal details such as your mother's maiden name or the street you grew up on.
Southworth suggests using memory tricks to remember different answers to the regular questions. If the question is, "What is your mother’s maiden name?", you might substitute your mother's favorite food.
Replace your phone and computer
If you've recently split with an ex whom you suspect was stalking you, and still have a computer or phone that he or she was once able to access, consider replacing the device.
"There are ways to detect if you've been compromised, but it's not going to point to who's doing it," said Leonard.
"If it's a situation where you want to know," Leonard said, "then we go through a forensic computer person who would do it either in the computer or on the phone itself to see if it's been compromised … The best thing is to go get another phone."
If you do get a new phone, don't let the phone company move your data from your old phone to the new one. If they do that, they'll move any spyware to the new phone along with everything else, Leonard said.
Instead, you should back up your photos, contacts, videos and other data with a backup service like Google+, the iCloud, or an independent service like Lookout or Instagram. These services know how to prevent malware disguised as media files from infecting their cloud storage.
Once you've moved these files from your old phone to the cloud, move them back to your new phone manually.
If you can't afford a new computer, then you should wipe the hard drive and reinstall the operating system, applications and personal data to make sure the device is clean.
First, back up all personal data, including images and documents, to another drive. Next, make sure you have the original installation media for the operating system, including verification codes, and the same for any paid applications. Then begin a full system-installation process, without retaining anything currently on the computer's hard drive.
You could also consider an entirely different operating system. If the spyware installed on your computer is designed to run in Windows, switch to Linux. This is a free, open-source operating system, so setting it up on your computer will cost nothing but your time.
Linux comes in hundreds of different versions; if you're looking for a very user-friendly version, consider Ubuntu Linux, Linux Mint or PCLinuxOS. Changing your operating system might be enough to stop your stalker in his or her tracks.
"When you get a harassing text, the knee-jerk reaction may be to delete it. However, when possible, saving the original electronic document is important," Southworth said. "Then his [or her] only defense is, 'Someone broke into my phone.'"
Every time someone sends you an abusive message, every time you see someone following you, every time you find evidence of someone surveilling you, write it down. Even if it's just a screenshot or a handwritten list of events, plus the date and time, it will help if you ever take your stalker to court.
You can find more resources at WomensLaw.org, a website designed to help victims of domestic violence and assault find help and support. For assistance with technology related to domestic abuse, check out techsafety.org, a technology summit co-hosted by the NNEDV that aims to educate people on digital surveillance and privacy issues.
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Jill Scharr is a staff writer for Tom's Guide, where she regularly covers security, 3D printing and video games. You can follow Jill on Twitter @JillScharr and on Google+. Follow us @tomsguide, on Facebook and on Google+.