Study Notes

MD5 invented by RSA data security company, is algorithm of checking summary.SHA1 is a hash algorithm,it runs slower than MD5.

Computer check md5 message digest:

#md5sum

Issue the above command,we could get a string created by md5 algorithm.If the file is modified,and we use md5sum command later,a different string would be created.This is always used to check file’s integrity and ensure the identified file is not modified.

How to identify the system has been invaded? We could estimate by the following situations:

1.Homepage of explorers has been modified.
2.Spaces of harddisk reduce rappidly.
3.Detecting contract from other administrators.
4.System’s log has been erased.
5.New account has been created.
6.There are unknown processes running.
7.CPU always work in high rate which can not be explained.
8.The remote account of localhost was detected by hackers.

And then,when we find this issues happen in our system,we should do the following step:

1.Shutdown the network service and change to single user mode by booting from floppy.
2.Estimate the degree of having been destoried.
3.Try to recovery online.