In his keynote address to the event, Osborne blamed foreign intelligence agencies for the attacks, which he said were mainly seeking to steal private information, most notably from the Treasury's computer systems.
"At some point last year, a perfectly legitimate G20-related email was sent to HM Treasury and some other international partners.
Within minutes it appeared that the email had been re-sent to the same distribution list. In fact, in the second email the legitimate attachment had been swapped for a file containing malicious code", he told his audience.
"To the recipient it would have simply looked like the attachment had been sent twice. Fortunately, our systems identified this attack and stopped it", he added.
Osborne then revealed that the government is investing heavility in research into the constant battle to better defend its servers.
According to Graham Cluley, senior technology consultant with Sophos, the "20,000 malicious emails sent to government networks" statistic is getting a lot of press, but it is actually the same as the one revealed last year by GCHQ.
"At that time it was claimed that 5% of the attacks (1,000 a month) were specifically targeted against government departments", he noted in his security blog, adding that, earlier in 2011, UK Home Secretary William Hague revealed that attackers had successfully infected government departments with Zeus.
"Of course, most of the attacks said to be hitting the UK government are hitting other organisations and businesses around the world too. Governments and firms alike face the challenge of keeping their systems secure, and their sensitive data out of the hands of cybercriminals", he observed in his security blog.
"It's unclear whether all UK government departments are now up-to-date in the browsers and other application they use, but it seems to me that if their computers are being attacked by foreign powers with booby-trapped documents and dangerous links that to do anything less would be negligent in the extreme", he noted.
Over at Guidance Software, meanwhile Frank Coggrave, the data forensics specialist's general manager for EMEA, said that there is more data and connectivity, across more institutions - covering more citizens - which makes for a target-rich environment for cyber criminals.
"With the increase in this data, the government must increase the levels of vigilance and protection. Even the best technology companies fall foul of the attackers and they have none of the complexity of modern government", he said.
"We support the Chancellor's plans to involve academia and the private sector in his search for solutions", he added.