Hotmail users have been warned over malicious spam that specifically targets the Microsoft webmail's users.

Trend Micro senior security analyst Rik Ferguson claimed that spam messages have been detected as arriving with text indicating that it has image file attachments in the JPEG format.

However the file names of attachments are actually links that connect to shortened URLs, which in turn connect to malicious URLs. Connecting to the malicious URLs, which are now blocked, leads to the download of the malicious file, which is now detected as TROJ_DLOADR.AQJ. This downloads a wide variety of information-stealing malware.

Trend Micro claimed that it is deceptive as the links were crafted to look very similar to how file attachments are displayed in most emails. An envelope-shaped icon is even seen at the side of each of the links, which is typical for file attachments.

Differences between such spam email and a legitimate email message, which users must watch out for should they receive a suspicious email message, include: the attachment details are indicated not in the message area, but above it, along with the other fields; the number of attached files are supposed to be stated right under the email address in the To: field; the size of the attached file is displayed beside the file name; and the attached images are always displayed at the bottom of the message.

Trend Micro advised Hotmail users to not click on any of the links contained in messages that do not display the above mentioned details.