DNS spoofing and poisoning mislead ordinary name lookup so people or systems are sent to an address the attacker alone chose.
DNS here means the Domain Name System, and a name server is a system that answers which address belongs to a name.
How it works
Spoofing presents a false answer as if a legitimate name server had given it.
Poisoning means a resolver stores that false answer and repeats it to later users, so the mistake outlives the first query.
The harm is that people or applications reach the wrong destination while believing the name was correct.
Defenders rely on resolvers they trust, on signed name data where it is deployed, and on certificates so a wrong address is harder to use for a quiet impersonation.
Concrete examples
- A traveler's browser is sent to a lookalike payment site because a local resolver cached a false address for a familiar name.
- An internal application reaches the wrong partner host after a resolver accepted an answer it should not have trusted.
- A certificate warning appears for a routine site, and the investigation finds the name answer pointed somewhere unexpected.
Protective measures
- Send your systems to resolvers you operate or explicitly trust, and block ad hoc resolver changes on managed devices.
- Deploy signed name answers where your domains support them, and monitor validation failures.
- Treat unexpected certificate warnings as a possible sign of a false name answer, not only as a browser glitch.
- After a suspected false answer, flush the affected cache and record which resolver accepted it.