Use of per-flow monotonically decreasing TTLs to prevent IDS circumvention
US7873731B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 8, 2004 |
| Grant date | Jan 18, 2011 |
| Priority date | — |
| Expiry date | Oct 16, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L63/1416
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Systems detect maliciously formed TCP/IP retransmit packets attempting to pass through an intrusion detection system (IDS) and prevent them from reaching their destination by forcing early flow termination. As each packet arrives in the IDS, the TTL field is monotonically decreased by setting it to the smallest TTL received from the packet flow. Any packet flow that attempts to confuse the sensor with a low TTL will be starved off and will never reach the destination host. Each flow may be periodically reset to a high value or to the current packet value to allow flow recovery. In another embodiment, the TTL decrease mechanism may operate on a contingent basis, determined by the presence or absence of the flow identifier on a pre-determined list of flows that should never be restricted.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.