Filipino and Malaysian hackers faced off online as a violent standoff between Malaysian forces and followers of the sultan of Sulu raged in Sabah.
Several Malaysian websites were crippled over the weekend by a group called "Anonymous #Philippine Cyber Army" after at least one Pinoy website had been defaced.
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Hackers using the name “Malaysia Cyb3r 4rmy” made the first attack Sunday, hitting the online sales portal of Philippines telecommunications giant Globe.
Visitors to the Globe website saw a black screen with a message saying "Do not invade our country or you will suffer the consequences."
Pinoy hackers launched a spate of attacks on Malaysian website in retaliation, crippling online portals using the .my domain until Monday.
Online users who opened the website of Malaysia's Stamford College, for instance, saw the dialog box which said "Philippines | #OpReclaim."
The hackers using the names "Kismet-07" ng "Anonymous Cebu" also warned Malaysian authorities against "illegally claiming" what they said was Philippine territory.
"Greetings Malaysia and Malaysian Govt. Time has come to reclaim what is truly ours," a message on the website read.
"Also, don't dare to hack our websites, OR ELSE WE WILL CONTINUE ATTACKING YOUR CYBER WORLD!" it said further.
The so-called "cyber war" comes after a standoff between Malaysian police and armed Filipino men since Feb. 9 turned bloody on Friday.
Violence is also feared to be spreading as followers of Sultan Jamalul Kiram III assert their ancestral claims over the Malaysia-governed territory.
Fresh clashes have been reported Sunday, with reports saying seven men--five Malaysian policemen and two from the Pinoy group--have been killed.