The telephone number 1-855-405-7156 is currently being used by cybercriminals to trick Yahoo users into calling it. If potential victims call the same telephone number they will be asked for their email account credentials (usernames and passwords) and may also be asked for credit card and other sensitive information. And, once the cybercriminals have gotten their victims' account and personal information, they will use it to hijack their accounts and use them fraudulently.
A Sample of a Fraudulent Email Asking to Call 1-855-405-7156
From: "Yahoo Mail Security" <64101602.9A89BBF23C4AC527406F33wphjkccuecukmxp@zegrsuljvewbjid.com>
Date: December 27, 2017 at 9:39:26 AM EST
Subject: Something is Wrong
We Have Detected Unusual Activity With Your Yahoo Account on Your Computer
Login Has Occurred on 12/25/2017 @ 11:43 PM EST
From IP: 34.125.12.1 Geo Location Found: Eastern Russia
If This Was Not You Please Call the Yahoo Security Team
(Be at your computer)
1 855-405-7156
Yahoo users who have already received the phishing email messages, and who have followed the instructions in them, are asked to change their Yahoo account passwords immediately before their accounts are hijacked by cybercriminals and used fraudulently. And, if they gave out their credit card information, they asked to contact their bank for help. They should let their banks know that they were tricked by a phishing email and unknowingly gave their credit card information to cybercriminals.