U.S. Democratic presidential candidate Hillary Clinton
© Carlos Barria / Reuters
Democratic presidential nominee Hillary Clinton's campaign and the Democratic Party's fundraising committee for its US House of Representatives candidates fell victim to cyber-attacks that are being investigated by the FBI, according to a Reuters report.

The Democratic Congressional Campaign Committee (DCCC) was the target of a cyber-attack in which a dummy website was registered as late as June to mimic a DCCC fundraising domain. The fake website directed donations away from ActBlue, the donation processing contractor working with the DCCC, according to a Reuters report.

What data was exposed is yet unclear, though various personal information including credit card details could have been accessed. Anonymous sources told Reuters that the hack may have been an attempt to cull information about DCCC donors rather than to steal money.

A computer network used by the Hillary Clinton campaign has also been hacked, law enforcement is confirming, making last week's hack of Democratic political organizations just the tip of the iceberg.

Private investigators hired by the Clinton campaign discovered that the network had been hacked into, CNN reported. While the campaign confirmed that their data program was accessed in the broader attacks on Democratic organizations, they claim that there is no evidence so far to indicate that their internal systems were compromised.

"An analytics data program maintained by the DNC, and used by our campaign and a number of other entities, was accessed as part of the DNC hack. Our campaign computer system has been under review by outside cyber security experts. To date, they have found no evidence that our internal systems have been compromised," campaign spokesman Nick Merrill told CNN.

The FBI made the Clinton campaign aware that it was being targeted by hackers back in March, Yahoo News reported, citing "two sources who have been briefed on the matter."

The FBI reportedly visited Clinton's campaign headquarters in Brooklyn, where agents told senior officials that the campaign had been subject to so-called spear-phishing email attack attempts, without specifying who was suspected of being responsible.

Yahoo News reported that the FBI had asked the Clinton campaign to hand over internal computer logs and the personal email addresses of senior campaign officials, but the request was denied by the campaign's lawyers, citing sensitivity and concerns that the FBI's request was too vague.

The fake website in the DCCC hack was the host to complex malware that can easily elude most antivirus monitors, cyber experts told Reuters.

"It's really rare malware," according to Justin Harvey, chief security officer with Fidelis Cybersecurity, suggesting the hack was unlikely to be the work of independent criminals.

ActBlue, the donation processing contractor for the DCCC, said none of its servers or customer information was compromised. The FBI only said that its investigation of the DNC hack is ongoing.

"The FBI is investigating a cyber intrusion involving the DNC and are working to determine the nature and scope of the matter. A compromise of this nature is something we take very seriously, and the FBI will continue to investigate and hold accountable those who pose a threat in cyberspace."

The Clinton campaign did not comment on the hack of its systems, only referring to previous claims that hacks targeting the Democratic Party are "a national security issue."