The Congressional Budget Office (CBO) has reportedly been hacked, with the breach now considered ‘ongoing’. Lawmakers and staffers have been warned to exercise caution in their communications, as both incoming and outgoing emails could be compromised.

The non-partisan agency is responsible for analysing US economic policy and preparing cost estimates for Congress. The breach threatens sensitive economic data that could influence policy decisions and trade negotiations.

While there have been suspected state-backed hackers, experts point out the vulnerabilities in the federal cybersecurity infrastructure more.

US Budget Office Suffers Cybersecurity Breach

In a report by Politico, the Library of Congress employees received an urgent notice advising them to avoid clicking on links in emails from CBO accounts and to refrain from sharing sensitive information via email, Microsoft Teams, or Zoom.

The advisory emphasised verifying communications by contacting the sender directly over the phone. Staffers have also been urged to maintain heightened vigilance, as the breach affects ongoing legislative scoring and cost analyses for bills in both the House and Senate.

The CBO’s work is central to Congress, providing lawmakers with impartial economic projections and assessments of proposed legislation. Its analyses cover everything from the president’s budget to long-term US fiscal trends, making its information potentially valuable to foreign intelligence services.

Suspected Chinese Involvement

While the Senate sergeant at arms did not name a culprit in a previous email, sources briefed on the hack indicated that Chinese state-backed actors are suspected, per CNN.

Beijing routinely denies cyberattack allegations. Liu Pengyu, a spokesperson for the Chinese Embassy in Washington, said ‘China consistently opposes and strictly combats all forms of cyberattacks in accordance with the law’.

Cybersecurity experts note that this incident is becoming a pattern. Earlier in 2025, suspected Chinese hackers targeted Wiley Rein, a law firm involved in advising the US government and private companies on trade issues.

These attacks appear focused on gaining intelligence about US policy decisions over ongoing trade tensions.

Federal Cybersecurity Affected by Government Shutdown

The ongoing record government shutdown, which reached over 40 days, has stretched federal cybersecurity resources.

The Cybersecurity and Infrastructure Security Agency (CISA), the main agency defending against cyberattacks, planned to furlough roughly two-thirds of its 2,540-person workforce at the start of the shutdown. Analysts warn that such resource constraints leave federal networks more vulnerable to state-backed and criminal hackers.

CBO’s breach could have serious consequences if sensitive economic data were exposed, as Congress relies on the agency for its federal budgeting, which is important in mending the record-breaking government shutdown. Any compromise could affect the transparency and integrity of the legislative process, while providing foreign actors with insights into US priorities and strategies.

Investigations of the breach are underway to implement new security measures, but officials acknowledge the challenge of fully restoring trust in communications. Lawmakers and staffers are still encouraged to remain vigilant as the threat remains live. The stakes for ignoring advisories include policy decisions, financial markets, and negotiations.

‘Staff must act as if every communication could be monitored until the breach is fully contained.’