Microsoft has killed Dell's user-pwning root certificate and its self-reinstalling .dll with its antivirus Defender tool.

The certificate is a big blunder because it opens a universal means for attackers on public networks to hose new Dell laptops.

That's because bright minds planted a self-signed root CA certificate and private key on new laptops which allows attackers on public Wi-Fi to steal otherwise encrypted usernames, passwords, and other sensitive data.

"An attacker can exploit a certificate using phishing or man-in-the-middle attacks to decrypt, modify or spoof HTTPS websites, such as banking, social media, or email websites," Microsoft bod Karthik Selvaraj says.

"This could allow a malicious hacker to steal your usernames, passwords, and confidential data.

"They could also carry out transactions without your knowledge, even when it seems like you have a secure browser connection to a website."

The free Windows Defender tool will kill the certificates and the associated Dell.Foundation.Agent.Plugins.eDell.dll plugin that will respawn the certificate.

Microsoft flags the Dell scourge as Win32/CompromisedCert.D. Windows 7 users can run Microsoft Security Essentials, or Redmond's Safety Scanner or Malicious Removal Tool.

Dell customers curious about their exposure can visit a test site setup by system admin Hanno Böck. ®