Lsass stands for Local Security Authority Services System. This program determines what kind of user you are, for example an Administrator. It also authenticates the validity of user logons. This program is critical in the stability and security of your computer. If you have an lsass error, there are two steps you need to take. Find out why you have the error, and second, correct the underlying problem.

First is to determine what is causing the error. The three main causes of lsass errors are a corrupted or missing dll code, a corruption in the lsass program itself, or a worm, virus, Trojan, spyware, adware, keylogger or other unwanted software. Deleting an unwanted or unused program can corrupt or even erase a dll file. Quite often several programs depend on the same dll file, and if it becomes corrupted or is missing these programs may not work properly, if they run at all. Prematurely halting, terminating or disabling the lsass program can corrupt the program and cause it to malfunction. The third cause of lsass errors is unwanted programs like worms adware, and keyloggers.

The best known worm that corrupts the lsass program is the Sasser worm. One sure method of determining whether or not the lsass error is caused by a worm or other malicious software is an infected PC will shutdown and and attempt to reboot about once a minute. The error message created by these malicious softwares will indicate a problem with the lsass program.
Once you have determined the cause of the lsass error, the next step is to correct .If the error is caused by malicious softwares, find and use a removal tool. These are often found in many reputable places online.

If, however, the problem is not related to any infection, you need to take a different approach. Think about any programs you have recently installed. With the exception of critical programs, consider uninstalling them and see if the problem is corrected. Likewise, consider any programs you may have recently deleted. Could the deleting process have damaged the lsass program or the associated dll code? The associated registry files will need to be repaired to solve this issue.
The Registry is the heart of the computer, and unless you are a computer heart surgeon, and completely sure of what you are doing, it is not recommended you attempt this repair without professional help.

There are many highly regarded registry scans available free on the Internet that can find and fix any errors. The safest answer is to download and run one of these programs.