my screen is flashing some time is it attacked by flashback virus?

Hello, I've never heard of that symptom for Flasback, but...

Disable Java in your Browser settings, not JavaScript.

http://support.apple.com/kb/HT5241?viewlocale=en_US

http://support.google.com/chrome/bin/answer.py?hl=en-GB&answer=142064

http://support.mozilla.org/en-US/kb/How%20to%20turn%20off%20Java%20applets

Flashback - Detect and remove the uprising Mac OS X Trojan...

http://www.mac-and-i.net/2012/04/flashback-detect-and-remove-uprising.html

In order to avoid detection, the installer will first look for the presence of some antivirus tools and other utilities that might be present on a power user's system, which according to F-Secure include the following:

/Library/Little Snitch

/Developer/Applications/Xcode.app/Contents/MacOS/Xcode

/Applications/VirusBarrier X6.app

/Applications/iAntiVirus/iAntiVirus.app

/Applications/avast!.app

/Applications/ClamXav.app

/Applications/HTTPScoop.app

/Applications/Packet Peeper.app

If these tools are found, then the malware deletes itself in an attempt to prevent detection by those who have the means and capability to do so. Many malware programs use this behavior, as was seen in others such as the Tsunami malware bot.

http://reviews.cnet.com/8301-13727_7-57410096-263/how-to-remove-the-flashback-ma lware-from-os-x/

http://x704.net/bbs/viewtopic.php?f=8&t=5844&p=70660#p70660

The most current flashback removal instructions are F-Secure's Trojan-Downloader:OSX/Flashback.K.

https://www.securelist.com/en/blog/208193454/Flashfake_Removal_Tool_and_online_c hecking_site

More bad news...

https://www.securelist.com/en/blog/208193467/SabPub_Mac_OS_X_Backdoor_Java_Explo its_Targeted_Attacks_and_Possible_APT_link

The "Flashback" malware had nothing to do with a screen flashing. The "flash" in Flashback was related to this malware first being found in sites that prompted users to install a fake flash (as in Flashplayer from Adobe), which then caused an infection.

When does the flashing screen happen? Can you relate it to something you are doing?

sachin wrote:

my screen is flashes sometime i worried about is there flashback virus is attacked my mac

Flashback redirects your browser to advertising web sites. It has never been known to act as you described.

sachin wrote:

my software update is not showing any update after i installed safari 6 on 30 of jul

Software Update only shows items it installed. Did you use Software Update to install Safari 6 or download it from the web site? In either case there will be a file in /Library/Receipts/boms/ named something like "com.apple.pkg.Safari..." with a date sometime in July.

Probably not this, but check it anyway - System Preferences > Universal Access > Hearing tab.

there is a checkbox to flash the screen when an alert is given.