The Royal Institute of British Architects' (RIBA) members database was hacked at the weekend, causing the institute to close access to the members' area, which remains shut.
RIBA reports that 1,200 other organisations in the US and UK have also been attacked in a similar way, but "neither the RIBA nor other organisations contacted have yet found any evidence of fraudulent activity or attempts to extract information from the databases".
According to a RIBA spokeswoman, the attacker "planted a web address on the databases. The source has been traced to an organisation in China known for its large scale spamming. We cannot be certain of the purpose but it is likely to be the capture of email addresses."
Technical staff at the institute spotted the problem and closed access to the database as a precaution.
RIBA sent an email on Thursday warning its 40,000 members to keep an eye on bank accounts and credit card statements that may have been used for payments to RIBA. However, it assured them there is no evidence that any information was stolen. It has also reported the incident to the Metropolitan Police.
The institute refused to comment on whether the database was encrypted or password protected.
RIBA chief executive Richard Hastilow said: "We are taking urgent action to upgrade the protection of our systems against this latest type of threat." ®