Email-Worm:W32/Mimail.I

Email-Worm:W32/Mimail.I is a worm that propagates in infected email attachments. Mimail.I also has a payload: it uses a fake web that appears to be a legitimate enquiry from Paypal, in order to steal credit card information.

F-Secure has received reports of emails containing the Mimail.I worm that use the attachment name: 'paypal.asp.scr'. As the worm is coded to send emails with the attachment name 'www.paypal.com.scr', it is likely that these new messages were hand-crafted.

Mimail.I was found on November 14th, 2003.

Infection

Mimail.I arrives in email that looks as follows:

If the user runs the attachment, Mimail.I copies itself to the Windows Directory as:

• svchost32.exe

This copy is added to the registry as:

• [HKLM\Software\Microsoft\Windows\CurrentVersion\Run\SvcHost32]

The worm also drops a fake web form to:

• c:\pp.hta
• c:\pp.gif

Propagation

Mimail.I uses its own SMTP engine it sends emails with the malicious attachment.

The worm collects email addresses from files on the infected computer. It recursively searches through the user's document folders and looks into all the files whose extension is not on the following list

• "bmp"
• "jpg"
• "gif"
• "exe"
• "dll"
• "avi"
• "mpg"
• "mp3"
• "vxd"
• "ocx"
• "psd"
• "tif"
• "zip"
• "rar"
• "pdf"
• "cab"
• "wav"
• "com"

To find the SMTP server of the target email address, the worm does an MX lookup using a predefined public DNS server.

The emails used by Mimail.I to distribute its infected attachment has the following characteristics:

• From: "PayPal.com" donotreply@paypal.com
• Subject: YOUR PAYPAL.COM ACCOUNT EXPIRES
• Attachment: www.paypal.com.scr
• Body text:

Dear PayPal member, PayPal would like to inform you about some important information regarding your PayPal account. This account, which is associated with this email address recipient@somewhere will be expiring within five business days. We apologize for any inconvenience that this may cause, but this is occurring because all of our customers are required to update their account settings with their personal information. We are taking these actions because we are implementing a new security policy on our website to insure everyone's absolute privacy. To avoid any interruption in PayPal services then you will need to run the application that we have sent with this email (see attachment) and follow the instructions. Please do not send your personal information through email, as it will not be as secure. IMPORTANT! If you do not update your information with our secure application within the next five business days then we will be forced to deactivate your account and you will not be able to use your PayPal account any longer. It is strongly recommended that you take a few minutes out of your busy day and complete this now. DO NOT REPLY TO THIS MESSAGE VIA EMAIL! This mail is sent by an automated message system and the reply will not be received. Thank you for using PayPal.

Payload

On executing the worm, a fake web form that appears to be from Paypal is displayed. This is a Social Engineering trick used by the worm to deceive users into entering their credit card information into the form.

Once entered, the credit card information from the form is collected to a file, 'c:\ppinfo.sys' which is later mailed to certain email addresses.