BloomGuard

Is this link a known phish?

Paste a link and BloomGuard checks it against PhishTank's list of known phishing sites. The list is stored in a Bloom filter, a compact way to test whether something is in a set.

Check a link

Try:
Phishing links stored
—
Filter size
—

Bits checked per link
—
False alarm chance
—

Report a phishing link

The link is added to the filter straight away. Bloom filters can't remove entries, so only report links you're sure about.

How it works

  1. Store

    Each phishing link is hashed to a few positions in a large array of bits, and those bits are set to 1. The links themselves aren't kept.

  2. Check

    A link you enter is hashed the same way. If any of its bits is 0, it is definitely not on the list. If all of them are 1, it probably is.

  3. Trade-off

    Bits take far less space than the links. The price is an occasional false alarm, when other links happen to have set all the same bits.