The European Parliament network has fallen under cyber-attack, leading to a suspension of webmail and other security restrictions.
The assault, which has led to the suspension of webmail access in Strasbourg, comes after attacks against the European Commission and the External Action Service networks.
The Parliament and the Commission run over separate networks. The attack on the parliamentary network was reportedly detected on 24 March, two days after problems with the Commission's Microsoft Exchange email server system first emerged.
An EU official said that the two attacks appeared to be co-ordinated, well-organised and geared towards extracting sensitive information. "This is not a couple of teenage boys hacking into the [EU] institutions," the official told European Voice.
Popular theory has it that Chinese state-sponsored hackers may be behind the attack but this remains, at best, supported by only circumstantial evidence.
A Register source at the EU has forwarded internal documents which reveal that eurotechnocrats and security experts at Microsoft and McAfee are puzzling over the attack, first detected a week before it was publicly disclosed.
"Large-scale activity at EC started on or around 9 March," the source told El Reg. "It was only spotted because Exchange system messages (including out of office messages) switched to Chinese on affected mailboxes as remote access happened.
"Remote mail was definitely compromised but it's likely that this runs much deeper. The vectors are unclear and some systems have been spontaneously uninstalling malware from themselves."
Early reports linked the timing of the assaults with an EU Council summit meeting where the subjects up for debate included Libya and the European economic crisis, a suggestion our source dismissed as cobblers, while acknowledging that the attack was deep-penetrating and serious.
"Suggestions that this attack is somehow related to current meetings at Council are bizarre to say the least," the source said. "Council has almost no users on the affected systems. Also saying that such attacks are business as usual is also not true. This is a major incident." ®