A clipboard hijacker is malware that watches your clipboard for a crypto address and silently swaps it for an address controlled by the attacker.
You copy the address you want to send to, and the malware replaces it with the attacker's address before you paste. If you do not notice, you send funds to the wrong place.
Crypto transactions are irreversible. Once sent to the wrong address, the funds are usually gone for good.
Always verify the full address after pasting, ideally by comparing several characters at both ends. Use a hardware wallet, which often lets you confirm the address on the device screen.
Keep your device clean of malware, avoid suspicious software, and use the wallet's own copy buttons from official apps.
Never trust a pasted address blindly. A quick visual check is the difference between a safe transfer and a total loss.