"Brother Xiao, I lost my 3 million U." The voice on the other end of the phone sounded incredibly desperate. "Just staring at the screen, the balance suddenly zeroed out... I didn't touch anything at all." This isn't a margin call or a contract explosion, it's pure asset theft. What's the problem with reporting to the police? The police say: "Maybe a family member accidentally operated it." Nonsense. Only after reviewing the surveillance logs later did I understand what happened—three-year-old unupdated phone system, WiFi password used for seven or eight years without change, mnemonic screenshot stored in the phone memo. Plus, installed a bunch of suspicious "financial advisor" apps. Everything was full of vulnerabilities. This is the most heartbreaking reality in the crypto world: you painstakingly build a "security door" that might be impenetrable, but the key is hanging openly on the doorknob. Over the past two years, I’ve been tracking hacker tactics and have seen too many such cases. The most I tell my friends is: learn how to "close the door" in the crypto space first, then think about bottom-fishing for profits. Too many people only chase hundredfold returns but guard their assets with cardboard walls. Today, I won’t talk about market trends or price fluctuations, just these three critical security rules: **First: Never store mnemonic phrases online** Many people save their mnemonic phrases in WeChat, memos, or even take photos and store them on their phones. What’s the difference between that and posting your house key on the community bulletin board? The correct approach is simple—find a piece of paper, write it down by hand, and store it in two separate secure locations. Never let it contact the internet. Once the mnemonic phrase leaks, your assets are at the mercy of others. **Second: Create a dedicated isolation zone for your wallet** If your assets are substantial, it’s best to prepare a separate clean device. This device should only be used for wallet operations, with no unnecessary apps installed, no clicking on links from strangers, and avoid connecting to public WiFi. Old devices have too many vulnerabilities and are really not suitable for storing heavy assets. **Third: Regularly update your online habits** Regularly change your home WiFi password and upgrade your router firmware promptly. You’d be surprised how many hackers sneak in through the home network. These seemingly insignificant details are often the last line of defense. To put it simply, we all like to talk about "how to earn faster," but few truly spend time studying "how to protect more steadily." In this world, security isn’t a multiple-choice question; it’s a life-and-death hurdle you must pass. Without proper security measures, no matter how much you earn, you’re just working for others.