The Polish Cyber Command announced the operation earlier this week, according to news outlets.
Microsoft said on Monday it had identified a "nation-state activity group" that exploited "the CVE-2023-23397 vulnerability" to supply "secret, unauthorized access" to email accounts within Exchange servers.
The US tech giant named the group as the Russia-based Forest Blizzard, Poland's wnp.pl website reported.
According to the Polish army, Forest Blizzard took "malicious actions against public and private entities in Poland."
In response, the Polish Cyber Command and Microsoft joined forces to "take action against Forest Blizzard" and to "identify and mitigate" techniques used by the group, according to officials.
Microsoft on Monday urged users to "ensure Microsoft Outlook is patched and kept up to date to mitigate this threat."
The US tech giant outlined the security steps to take, and the Polish army provided instructions for users.
Microsoft has described Forest Blizzard as "a Russian state-sponsored threat actor that primarily targets government, energy, transportation, and non-governmental organizations in the United States, Europe, and the Middle East."
Forest Blizzard is linked to Russia's military intelligence agency GRU, according to the US and UK governments.
Figure: Polish Army
Source: PAP, Polish Army, Microsoft, wnp.pl