Servers at the World Bank have been repeatedly breached for more than a year by different intruders, according to Fox News in the US.
It is not clear how much data might have been compromised in the attacks, the TV channel said. The World Bank is contesting details of the story, which quoted unnamed sources as saying the banking group was hit by at least six major intrusions from the summer of 2007 until this September.
At least two of the intrusions appear to have originated from the same batch of IP addresses within China, the report said.
The first of the intrusions, from China, was discovered in September 2007 when the FBI apparently informed the bank of the problem which it discovered while it was conducting an unrelated investigation.
It apparently allowed the perpetrators to gain full and complete access to a secret data hub maintained by the organisation in Johannesburg, South Africa for a period of at least six months, the Fox News story said.
Another of the breaches, this time involving the bank's treasury network in Washington DC, appears to have been perpetrated by a contractor or contractors working for India's Satyam Computer Services, the story said.
The Satyam employee or contractor infected some workstations at the banks headquarters in Washington with keystroke logging software, which then sent any information it captured to a still unknown location.
Following the discovery of the breach, the World Bank Group immediately shut down its communication link with Satyam's offshore development centre in Chennai, India.
Satyam, one of India's largest IT services companies, has been handling several IT services functions for the World Bank since July 2003. The contract was due to be renewed this September but was allowed to lapse.
Jim Swords, a US-based spokesman from Satyam, declined to comment on the status of the contract with the World Bank. He read a prepared statement that in essence neither confirmed nor denied the details in the Fox report.
"Upon learning of this report today senior executives initiated an internal investigation to determine the validity of these claims, however unlikely. We will share the findings of the investigation at the conclusion of these efforts," the statement said.
Another pair of intrusions, in June and July, originated from the same group of IP addresses in China as the first attack had come from.
This time, however, whoever was behind the attack first compromised an external server run by one of the bank's units and used it to gain access to a server belonging to the Multilateral Investment Guarantee Agency (MIGA), the World Bank's insurance arm.
The hackers used their access to basically map out the entire system topography, including the types of servers and the types of files on the servers, the Fox report said, quoting an unnamed insider.
The story also contained a link to a purported internal World Bank memo, dated July 10, that appeared to be an update to some staff about the June/July server breach.
The memo noted that a "minimum of 18 servers had been compromised in total, including a domain controller, the main authentication server and a Human Resources server containing scanned images of staff documents.
In total, five of the compromised servers contained sensitive data, the memo noted. The intrusions appear to have been the work of someone using an senior system's administrator's account to gain access.
The story portrayed the breaches as having triggered an extensive internal investigation by the World Bank's technology group and least two security assessments by external firms.
A spokeswoman at the World Bank asked us to submit a request for comment via email, but then did not respond to two subsequent messages seeking clarification on the initial news report.
However, in a response apparently sent to Fox News after it ran the story, the bank said the story was wrong and riddled "with falsehoods and errors". It also said the unnamed sources had provided misinformation, and that the leaked emails that were linked to the Fox story had been taken out of context.
The World Bank has also sought to downplay the seriousness of the intrusions by saying that it has been repeatedly attacked in the past, but at no point had any sensitive or personnel information been compromised.