Microsoft said hackers targeted European think tanks and non-profit organizations which often have contact with government officials.
The attacks were carried out late last year through phishing campaigns to steal employee credentials and deliver malware, the tech giant said in a blog post on Wednesday.
The company said it detected attacks targeting employees of the German Council on Foreign Relations and European offices of The Aspen Institute and The German Marshall Fund through malicious websites and spoofed email addresses that looked legitimate.
"The attacks against these organizations, which we're disclosing with their permission, targeted 104 accounts belonging to organization employees located in Belgium, France, Germany, Poland, Romania, and Serbia," Tom Burt, corporate vice president for customer security and trust at Microsoft, wrote in the blog post.
The German Marshall Fund runs a tool, known as the Hamilton 68, which tracks Russian propaganda and disinformation efforts online in near real-time. Karen Donfried, president of The German Marshall Fund, said in a statement Wednesday that the attacks "came as no surprise."
"Everything we do as an organization, from our policy research to our work strengthening civil society, is dedicated to advancing and protecting democratic values," Karen Donfried, president of The German Marshall Fund, said in a statement Wednesday.
"The announcement serves as a reminder that the assault on these values is real and relentless."