yammer.com Domain Breach Exposure Report

The telemetry indicates a significant exposure event impacting yammer.com, with a risk score of 100. The primary concern stems from 94,065 historical data breaches and 9,851 active infostealer logs, affecting over 103,000 clients and 517 employees. The data breaches constitute 90.5% of the observed events, while infostealer logs represent 9.5%. The timeline shows a surge in employee-related events in January 2026, with 407 instances, and a substantial increase in client-related events in March 2026, totaling 30,753. Malware families associated with these events include Redline (19.1%), LummaC2 (15.8%), and Rhadamanthys (9.6%), all known for credential theft. The exposure is primarily linked to combolist sources (99.5%) and database dumps (0.5%), suggesting compromised credentials are being widely distributed. The prevalence of infostealer malware targeting services like yammer.com and its login pages, coupled with the high volume of data breaches and active infostealer logs, indicates a high risk of account compromise and potential further downstream impacts. Remediation should focus on credential hygiene, multi-factor authentication enforcement, and active monitoring for unauthorized access attempts related to employee and client accounts.