Malware authors have made Microsoft's PowerPoint their vector of choice for infecting corporate systems.
Microsoft Word was the top choice for malware authors last year looking to embed code in seemingly innocuous documents.
But research from MessageLabs suggests that increased patching of Word, and a slack attitude to patching other applications, has prompted hackers to target PowerPoint.
"People expect to find PowerPoint in their emails, more so than applications like spreadsheets," said Alex Shipp, senior antivirus technologist at MessageLabs.
"Also it was a relatively untapped area and there were lots of exploits out there as Microsoft wasn't fixing them very quickly. Microsoft is now patching all these exploits that are brought out at a similar rate to Word."
The research found that PowerPoint now hosts 45 per cent of attacks, compared to 35 per cent in Word documents.
The most common targets were public sector systems, followed by the electronics and aviation sectors.
Surprisingly hackers are not attacking financial companies, although this may be because of improved security measures.
"There is not enough data but I think this is because if they try and steal directly from banks too many alarms go off," said Shipp.
"But where public sector institutions are involved there's a market for the data they hold."
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