Users of pirated copies of Windows XP may not be able to install Service Pack (SP2), as Microsoft has blacklisted the 20 most-copied discs.
According to Microsoft, users who have the same serial number as the 20 most-copied Windows XP discs will be unable to install the new upgrade.
But with the company blocking only these discs, some users of pirate copies will still be able to download the service pack.
The same tactic was used to stop users of pirate copies from installing SP1, although pirates then launched a tool to get round the anti-piracy measures.
"Microsoft really wants to limit the scope of attacks and this reflects the strategy. It's not altruistic by any manner of means," said Professor Neil Barrett, technical director of Information Risk Management.
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