The town of Vienna, Virginia this week confirmed it notified 811 people of an August 2025 data breach that compromised names, Social Security numbers, financial account info, and passport numbers.
Ransomware group Cephalus took credit for the breach.
Vienna officials have not verified Cephalus’ claim. We do not know if the town paid a ransom, how much Cephalus demanded, or how attackers breached Vienna’s network. Comparitech contacted Vienna officials for comment and will update this article if it replies.
“On or about August 14, 2025, the Town became aware that it was the victim of a data incident,” says Vienna’s notice to victims. “To date, our investigation revealed that malicious actors gained access to the Town’s network on or about August 11, 2025, and deployed ransomware to encrypt portions of the network.”
The notice does not mention any offer of free credit monitoring or identity fraud insurance, which are commonly offered to victims following a breach that includes Social Security numbers.
Who is Cephalus?
Cephalus is a new ransomware group that started listing targets on its data leak site in August 2025. The group exploits remote desktop (RDP) connections to compromise accounts that lack multi-factor authentication.
It has made 18 attack claims in total, two of which have been acknowledged by the targeted organizations. They include healthcare companies, manufacturers, legal firms, and other service-related businesses.
Cephalus’ other confirmed attack hit SystemEXE, a Japanese software developer. The company disclosed a June 2025 attack in which Cephalus claimed it stole 30 GB of data.
Ransomware attacks on US government
Comparitech researchers have logged 56 confirmed attacks against US government entities in 2025 to date.
Nine of those attacks occurred in August 2024. They include:
- Box Elder County, UT confirmed a data breach disrupted city services. Ransomware group Interlock claimed responsibility.
- West Chester Township, OH announced a cybersecurity breach for which ransomware group PEAR took credit.
Ransomware attacks can both steal data and lock down computer systems. Organizations must pay a ransom for the data and to restore systems, or else they face extended downtime, permanent data loss, and putting data subjects at increased risk of fraud.
About Vienna, VA
Vienna is a city of 16,473 people in Fairfax County, Virginia. It is a suburb of Washington, D.C.
