Malware
Parked domain
Parked domain is a registered name that points at a placeholder page, an ad page, or nothing. It is not malicious by itself, but it is a cheap place to stage something later.
How it is measured
Resolve the name and fetch it. Parking shows as A records at a registrar or parking-service IP, a generic 'this domain is for sale' page, an ad-only page, or an empty response. Check WHOIS or RDAP for registration date and nameservers, and certificate transparency logs for any certificate issued.
Watch for change. Record the DNS answer and a hash of the page daily. A parked name that suddenly gets new nameservers, a fresh certificate, or a live script is the moment of interest.
Worked example
A shop's security tool lists 'cdn-assetz.example' in its script allowlist, left over from a 2021 theme demo. A DNS lookup shows the name sat on a parking nameserver for two years serving a for-sale banner. Last week the A record changed to a VPS address and /lib.js appeared.
Nothing was attacking anyone while the name was parked. Once /lib.js began serving a skimmer, every page that still referenced the old host was exposed. Removing the stale reference was a one-line theme edit.
How it differs
A DGA generates many throwaway names algorithmically so malware can find its controller; most are unregistered, and the few that are registered may sit parked until needed. A parked domain is one specific name that is idle. DGA is about how names are produced; parked describes what one name is doing now.
Common errors
Assuming a parked page means the domain is safe forever. Leaving parked or expired hostnames in script tags, CSP lists, and email records. Forgetting to renew a domain you once used for assets and letting a stranger register it. Treating every ad-filled page as an attack. Checking only the web page and ignoring MX records.
In practice
Grep your site for every external hostname, then check which ones are parked, expired, or unreachable. Remove references to dead hosts, and renew any domain you still rely on with auto-renew. If you retire a hostname on purpose, keep it registered until no page or email setting points to it.