How I can clean My I mac??

There are no extant viruses to clean. But see the following:

Helpful Links Regarding Flashback Trojan

A link to a great User Tip about the trojan: Flashback Trojan User Tip

A related link in the tip to a checker: Malware Checker Dowload Link

A Google search can reveal a variety of alternatives on how the remove the trojan should your computer get infected. This can get you started.

For now I recommend the User Tip from etressoft to detect and remove:

Checking for and removing the "Flashback" trojan

Kaspersky Flashback Trojan Site:Flashback Trojan Detection and Removal

Also see Apple's article About Flashback malware.

ClamXAV, free Virus scanner...

http://www.clamxav.com/

Free Sophos...

http://www.sophos.com/products/enterprise/endpoint/security-and-control/mac/

Little Snitch, stops/alerts outgoing stuff...

http://www.obdev.at/products/littlesnitch/index.html

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

Removal for 10.5...

http://support.apple.com/kb/DL1534