A computer hacker is a computer expert who uses their technical knowledge to achieve a goal or overcome an obstacle, within a computerized system by non-standard means. Though the term hacker has become associated in popular culture with a security hacker – someone who utilizes their technical know-how of bugs or exploits to break into computer systems and access data which would otherwise be unavailable to them – hacking can also be utilized by legitimate figures in legal situations. For example, law enforcement agencies sometimes use hacking techniques in order to collect evidence on criminals and other malicious actors. This could include using anonymity tools (such as a VPN, or the dark web) to mask their identities online, posing as criminals themselves. Likewise, covert world agencies can employ hacking techniques in the legal conduct of their work. Oppositely, hacking and cyber-attacks are used extra- and illegally by law enforcement and security agencies (conducting warrantless activities), and employed by State actors as a weapon of both legal and illegal warfare.