Having your identity stolen can be a nightmare, and cleaning up the mess can take months. You can make life difficult for a would-be identity thief by locking down these five key aspects of your online life. What happened to my ZDNet colleague Matthew Miller this month is the stuff nightmares are made of. The title pretty much says it all: "SIM swap horror story: I've lost decades of data and Google won't lift a finger." In Matthew's case, hackers were able to convince T-Mobile to issue a replacement SIM that gave them access to his primary phone number. That, in turn, allowed them to reset passwords on his Gmail account, which pretty much gave them unfettered access to his entire identity. They then proceeded to shut down his Twitter account, wipe out everything associated with his Google account, and even access his online banking accounts. As I read Matthew's story, I had flashbacks to a similar incident that happened to Mat Honan back in 2012. Honan, who's now San Francisco Bureau Chief for Buzzfeed, documented his excruciating experience at the time in a memorable Wired article: "How Apple and Amazon Security Flaws Led to My Epic Hacking." The lesson from both of these horrifying experiences is that your primary phone number and your primary email address are far more valuable than you think. As our reliance upon online services grows, these two data points are extremely common means of authentication. If either one is compromised, an attacker can do bad things. And if those two factors are tied too closely together, it's game over for your online identity. You don't have to be the next victim. With a little effort (and, yes, a little expense), you can lock down the security of crucial online services. Follow these five guidelines and you can make life extremely difficult for a would-be identity thief. Fight hackers with 5 security safeguards we have posted on OUR FORUM.