"Two unauthorized programs were found on the server, and our preliminary investigations indicate that these were designed to allow unauthorized remote access to information," announced the company, and added that they have taken the server in question offline for the time being.
A forensic investigation and an in-depth audit of the server was ordered, but it is still unknown whether the information contained in the database was exfiltrated by the attackers.
According to the firm's notification, the attack was detected on April 3, when the attacker tried to upload two hacking tools - a password stealer and a privilege escalation tool - to the server.
"No financial information was stolen from this database," states the company. "This was not a database designed to hold financial information, but we ran comprehensive data scans to look for any banking details (credit cards, sorting codes, account numbers, etc.) lurking in the fields. All scans came back clean."
Data included in the server's databases include partners' names and business addresses, email addresses, contact details, and hashed passwords.
Taking that into consideration, Sophos has warned its partners about the possibility of receiving targeted phishing emails purportedly coming from the company.
The partners that have already switched to the new Salesforce-based portal have nothing to worry about, as it is hosted on another server.
The rest of them will be forced to change their passwords once the portal is back online, and are advised to change their passwords on other online accounts if they used the same one.