Method and systems for computer security

1. A method for maintaining computer security, comprising:

detecting a connection failure, wherein a potentially-infected machine attempts to connect to a target machine through a router, and wherein the connection failure is identified by a ICMP destination unreachable message, and wherein the ICMP destination unreachable message comprises a destination address and a corresponding source address, the destination address identifying the potentially-infected machine;

storing information relating to the connection failure with information relating to previous connection failures, the stored information including, for each destination address, a timestamp, a corresponding source address, and a destination port for the corresponding source address;

removing from storage at least a portion of the information relating to the previous connection failures if it is determined that the at least a portion of the information relating to the previous connection failures has been stored for a predetermined period of time;

determining a number of stored connection failures;

determining whether a machine is potentially infected with malicious code based on the determined number of stored connection failures; and

identifying an infection and a targeted service based on the stored information in response to determining that a machine is potentially infected with malicious code.

2. The method of claim 1 , wherein the ICMP destination unreachable message comprises the destination address and the corresponding source address, the source address identifying the router that sent the ICMP destination unreachable message.

3. The method of claim 2 , wherein the corresponding source address identifies the router that attempted a connection for which the connection failure occurred.

4. The method of claim 2 , wherein storing the information relating to the connection failure comprises determining whether the destination address is already stored.

5. The method of claim 4 , further comprising determining whether the corresponding source address is already stored if the destination address is already stored.

6. The method of claim 5 , wherein the corresponding source address is stored only if it is determined that the corresponding source address is not already stored.

7. The method of claim 6 , wherein removing at least a portion of the information comprises determining how long a corresponding source address has been stored and removing the corresponding source address if it is determined that the corresponding source address has been stored for a predetermined period of time.

8. The method of claim 7 , wherein a counter is incremented for each corresponding source address that is stored and decremented for each source address that is removed.

9. A system for maintaining computer security, comprising:

a processor; and

a computer recording medium including computer executable code readable by a computer, embodying a program of instruction executable by the processor, the computer executable code operable to execute:

a system for detecting a connection failure, wherein a potentially-infected machine attempts to connect to a target machine through a router, and wherein the connection failure is identified by a ICMP destination unreachable message, and wherein the ICMP destination unreachable message comprises a destination address and a corresponding source address, the destination address identifying the potentially-infected machine;

a system for storing information relating to the connection failure with information relating to previous connection failures, the stored information including, for each destination address, a timestamp, a corresponding source address, and a destination port for the corresponding source address;

a system for removing from storage at least a portion of the information relating to the previous connection failures if it is determined that the at least a portion of the information relating to the previous connection failures has been stored for a predetermined period of time;

a system for determining a number of stored connection failures;

a system for determining whether a machine is potentially infected with malicious code based on the determined number of stored connection failures; and

a system for identifying an infection and a targeted service based on the stored information in response to determining that a machine is potentially infected with malicious code.

10. The system of claim 9 , wherein the ICMP destination unreachable message comprises the destination address and the corresponding source address, the source address identifying the router that sent the ICMP destination unreachable message.

11. The system of claim 10 , wherein the corresponding source address identifies the router that attempted a connection for which the connection failure occurred.

12. The system of claim 10 , wherein storing the information relating to the connection failure comprises determining whether the destination address is already stored.

13. The system of claim 12 , further comprising a system for determining whether the corresponding source address is already stored if the destination address is already stored.

14. The system of claim 13 , wherein the corresponding source address is stored only if it is determined that the corresponding source address is not already stored.

15. The system of claim 14 , wherein the system for removing from storage at least a portion of the information comprises a system for determining how long a corresponding source address has been stored and removing the corresponding source address if it is determined that the corresponding source address has been stored for a predetermined period of time.

16. The system of claim 15 , wherein a counter is incremented for each corresponding source address that is stored and decremented for each source address that is removed.

17. A non-transitory computer recording medium including computer executable code for maintaining computer security, comprising: code for detecting a connection failure, wherein a potentially-infected machine attempts to connect to a target machine through a router, and wherein the connection failure is identified by a ICMP destination unreachable message, and wherein the ICMP destination unreachable message comprises a destination address and a corresponding source address, the destination address identifying the potentially-infected machine; code for storing information relating to the connection failure in a database with information relating to previous connection failures, the stored information including, for each destination address, a timestamp, a corresponding source address, and a destination port for the corresponding source address; code for removing from the database at least a portion of the information relating to the previous connection failures if it is determined that the at least a portion of the information relating to the previous connection failures has been stored for a predetermined period of time code for determining a number of connection failures stored in the database; code for determining whether a machine is potentially infected with malicious code based on the determined number of connection failures stored in the database; and code for identifying an infection and a targeted service based on the stored information in response to determining that a machine is potentially infected with malicious code.

18. The non-transitory computer recording medium of claim 17 , wherein the ICMP destination unreachable message comprises the destination address and the corresponding source address, the source address identifying the router that sent the ICMP destination unreachable message.

19. The non-transitory computer recording medium of claim 18 , wherein the corresponding source address identifies the router that attempted a connection for which the connection failure occurred.

20. The non-transitory computer recording medium of claim 18 , wherein the code for storing the information relating to the connection failure comprises code for determining whether the destination address is already stored.

21. The non-transitory computer recording medium of claim 20 , further comprising code for determining whether the corresponding source address is already stored if the destination address is already stored.

22. The non-transitory computer recording medium of claim 21 , wherein the corresponding source address is stored only if it is determined that the corresponding source address is not already stored.

23. The non-transitory computer recording medium of claim 22 , wherein the code for removing from the database at least a portion of the information comprises code for determining how long a corresponding source address has been stored and removing the corresponding source address if it is determined that the corresponding source address has been stored for a predetermined period of time.

24. The non-transitory computer recording medium of claim 23 , wherein a counter is incremented for each corresponding source address that is stored and decremented for each source address that is removed.