it's nly for knowledgebase i need to confirm that virus is attack on registry files?

what impact?

A virus can change or delete crucial registry files. Most of the time it add a startup registry key for itself to start every time the PC is booted up.

Yes virus can be impact registry file.

Most common registry key to check while dealing with Virus issue

http://www.symantec.com/connect/articles/most-common-registry-key-check-while-dealing-virus-issue

Virus attacks on registry may be designed to tamper the values stored in the registry - as a result depending on the values changed either it can start some of the malware with system start or in most serious cases may cause slow down of the system, corrupt software, etc.

These are the common load points for viruses on Registry

Common loading points for viruses, worms, and Trojan horse programs on Windows 2000/XP/2003

http://www.symantec.com/business/support/index?page=content&id=TECH99331

Hello,

Yes, Numerous threats attack SEP in an attempt to gain access to protected machines.

You could Harden Symantec Endpoint Protection (SEP) with an Application and Device Control Policy to increase security and this Protects Symantec Endpoint Protection files and registry keys

http://www.symantec.com/docs/TECH132337

 This rule set protects SEP's registry keys, files, processes and services from outside interference.  Enabling this rule could interfere with any non-Symantec products that attempt to integrate with SEP.

Hope that helps!!

What impact?

A lot ... certains thing could be disabled, changed or even deleted?

Most common is to add persistent effect to the the malware itself or disabling task manager and right click at folders..

Thanks Rafeeq for this info. Even if this doc is not recent , the content is still valid and helpful to understand the impact of a virus attack.