Reads the DKIM public key published at <selector>._domainkey.<domain>: key type, whether it is revoked (empty p=), decoded key size in bytes and a strength hint (about 1024-bit vs 2048-bit RSA), and basic syntax (v=DKIM1). Follows one CNAME, which large providers use. Does not check a signed message.

Spamhaus blocklist check through Spamhaus's official Data Query Service: an IPv4 address against ZEN (SBL spam sources, CSS snowshoe, XBL exploited/botnet hosts, DROP hijacked ranges, PBL end-user ranges) or a domain against the Domain Block List (spam, phishing, malware, botnet C&C, abused legitimate domains). Returns listed yes/no, every return code with the list it means, and Spamhaus's lookup link. Point-in-time answer.

From Shodan's pre-collected passive scan data: whether TCP port 22 was seen open on an IPv4 address and any OpenSSH version identified in its software (CPE) list. This is passive and may be days old; it is not a live SSH banner grab or algorithm audit.

Shodan InternetDB summary for an IPv4 address (free, no key): open TCP ports, host names seen, CPE software identifiers, tags and CVE IDs Shodan associates with the host. Data is from Shodan's last scan, so it can be days old; an IP with no data returns empty lists with known=false.

HTTPS certificate chain and cipher audit for a host (port 443) from Qualys SSL Labs' cached report: grade, number of certificates in the chain, trust store, TLS versions, weak-cipher count, Heartbleed/POODLE/BEAST flags and HSTS. Only reads reports SSL Labs already has, so a host that was never scanned returns a retry error instead of a new scan.

Checks an IPv4 mail-sending address against the SpamEatingMonkey DNS blocklist (bl.spameatingmonkey.net) through public DNS. A listed address returns its 127.0.0.x return code; an unlisted one returns no record. Listings change often; this is a point-in-time answer.

Checks Shodan's passive scan records for TCP port 445 (SMB) on an IPv4 address. Says whether SMB was seen open and when the record was last refreshed by the host data (not a live test). An address with no Shodan record returns seen=false with known=false; that is not proof the port is closed.

For a subdomain: finds its CNAME, matches the target against the public can-i-take-over-xyz fingerprint list (services such as GitHub Pages, S3, Azure, WordPress), checks whether the target still resolves, and fetches the subdomain once to look for the service's 'unclaimed' page text. Verdicts are evidence, not proof; the list is community-maintained.

Checks a domain against SURBL's multi-list (multi.surbl.org): whether it appears in spam or phishing URI lists. Listed domains return a 127.0.0.x code. Not listed means not in SURBL's current lists, not that the domain is safe.

Checks a URL or host against the OpenPhish public phishing feed (about 300 currently active phishing URLs, updated continuously). Returns whether the exact URL or any URL on the same host is listed, the feed size and up to 5 example URLs. Not listed does not mean safe; the feed is short and changes fast.

Reports whether Shodan's pre-collected passive scan data shows SNMP (UDP port 161) seen open on an IPv4 address. Passive and possibly old; no community string is tried, so default or public community access is not tested.

Reads a site's Referrer-Policy header and its <meta name=referrer> tag from the home page, works out the policy a browser would apply, and rates how much of the URL it sends to other sites (strict, moderate or leaky). One GET; links on other pages can set their own policy.

Checks Shodan's passive scan records for TCP port 3389 (RDP) on an IPv4 address. Says whether RDP was seen open (not a live test, and the record can be days old). An address with no Shodan record returns seen=false with known=false; that is not proof the port is closed.

Looks one http or https URL up in the PhishTank phishing database (live checkurl lookup, no key). Returns whether PhishTank has the URL and, if so, its phish id, verification flag and validity. Absence means PhishTank has no record of this exact URL, not that it is safe.

Reverse DNS (PTR) names for an IPv4 address, and forward-confirmed reverse DNS: whether each PTR name resolves back (A record) to the same address. Up to 3 PTR names are checked. Many addresses have no PTR record; that is a normal answer.

Checks the live HTTP response headers of a site's home page (one GET, https) for Content-Security-Policy, Strict-Transport-Security, X-Content-Type-Options, X-Frame-Options, Referrer-Policy, Permissions-Policy and Cross-Origin-Opener-Policy. Returns present/missing headers with their values and a score out of 7. It does not judge the quality of the values.

DataCite DOI search (public REST API, no key): DOI, title, publication year, resource type, publisher, creators and landing page for datasets, software and other research outputs. Metadata only.

Top 50 dapps from DappRadar's public rankings page: rank, name, token symbol, chains, market cap, token price, price change, trading volume, unique active wallets (UAW) and TVL, for 24h/7d/30d, optionally for one chain (eth, solana, bnb, base, polygon, arbitrum, tron...). Values in USD as shown by DappRadar; missing values are null. Public page, no key.

Checks a certificate SHA-1 fingerprint (40 hex characters) against the abuse.ch SSL Blacklist of certificates seen on malware botnet C2 servers. A hit returns the date added and the malware reason from the list. Only certificates this list tracks are covered.

US Department of Justice press releases from the justice.gov public RSS feed (keyword filter on title/summary). Latest items only. Public feed, no key.