Smartphone theft just got a whole lot less lucrative. Yesterday, California Governor Jerry Brown signed a bill requiring that all smartphones sold in the state include a “kill switch,” software that makes it impossible for thieves to use stolen phones. Here’s something you may not know: Your phone could already have such a switch. Both iPhones and Samsung phones have new software that “locks” the device so that unauthorized users are unable to activate it. According to the San Francisco Police Department, the city saw a 38% drop in iPhone thefts in the six months after Apple released its kill switch. In June, Google and Microsoft promised to offer kill switch technology in their next operating systems, and for now, both offer other apps to help you protect a lost phone. The California bill requires that tech companies make the kill switch feature standard on all phones starting July 1, 2015. In the meantime, you can enable your phone’s available security features by turning on the right settings. Here’s how. iPhones Do this right now: Make sure you have iOS7 software (if you haven’t already, you can download the upgrade on iTunes). Go to Settings, then iCloud, and then flip on “Find My iPhone.” If your phone gets lost, you’ll be able to track it on icloud.com. Do this if your phone gets stolen: Go to icloud.com/find and sign in using your Apple ID and password. There, a button lets you play a sound on your iPhone to help you locate the device. You can also put the phone in “lost mode,” which gives you the option to display an alternate phone number and a message explaining that the phone has been lost, so Good Samaritans will be able to find you. If you’re sure your phone has been stolen, erase the data. Remember that this is a last resort: Once you’ve erased your phone, you won’t be able to track it. But that way, the only way someone will be able to activate it is by entering your Apple ID and password. (And in the event that you find your phone again, you can restore the data using iCloud backup.) Android Do this right now: Android doesn’t have a kill switch yet, but it has still some helpful anti-theft features. Start by downloading the free “Android Device Manager.” Do this if your phone gets stolen: Sign in to the Android Device Manager using your Google account and password. Again, you’ll be able to play a sound, track your phone, reset the screen lock PIN, and erase the data. (Remember, once you erase the data, you won’t be able to track the phone anymore.) However, hackers may still be able to reset and reactivate the device. Expect a tougher kill switch feature in Google’s next software upgrade. Samsung Do this right now: If you’ve got a Samsung Android phone, you’re in luck. Go to Apps, then Settings, and then Security. Check the box next to “reactivation lock.” You’ll be prompted to either sign in to your Samsung account or create one. Do this if your phone gets stolen: Go to findmymobile.samsung.com and log in with your Samsung account. Like “Find My iPhone,” Samsung lets you track your phone, play a sound to help you find it, and lock your device remotely. If your phone has been jacked, the reactivation lock renders it useless. Once you’ve turned the feature on, no one can reset the device without your Samsung account and password. Windows Phone Do this right now: Windows phones don’t have kill switches yet either, but they do have a device tracking feature. Go to Start, then App, then Settings, and then “Find My Phone.” You can opt to save your phone’s location every few hours, which could give you a more accurate reading of its last known location if the battery dies. Do this if your phone gets stolen: Go to windowsphone.com and sign in with your Windows Live ID. You’ll be able to track your phone, play a sound, lock your phone with a message, and erase your data. Windows also plans to add a kill switch in the future.