Active e-mail filter with challenge-response
US8924484B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jul 16, 2002 |
| Grant date | Dec 30, 2014 |
| Priority date | — |
| Expiry date | Jul 5, 2024 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L51/42
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
When a user receives potential junk e-mail from an unknown sender address, an active filter installed in or cooperating with the user's e-mail system sends a challenge e-mail back to the sender address. Unless the user receives a correct response e-mail from the sender address and/or a response that meets formal criteria, the active filter rejects the original e-mail and blocks future e-mail from that sender address. The challenge preferably includes a question that the sender must correctly answer in his response. The question is such that only humans can interpret and respond to it correctly. For example, the question may relate to and/or be incorporated in an image in the challenge. Lists of approved and blocked sender addresses are compiled. The user may directly enter addresses in the address lists. Addresses to which the user has sent e-mail may also be included directly in the approved list.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.