PG & E Corp. shares jumped $ 1.63 or 8 percent to $ 21.03 on the New York Stock Exchange on Friday .
The stock rose $ 2.11 , or about 11 percent , to close on Friday at $ 21.51 on the New York Stock Exchange .
The virus spreads when unsuspecting computer users open file attachments in emails that contain familiar headings like " Thank You ! " and " Re : Details " .