Yahoo tackles large 'malvertising' campaign in its ad network

Ads with malicious code may have appeared across Yahoo's sites

Yahoo Corporate building in the daytime

Yahoo Corporate building in the daytime

Yahoo said Monday it had removed malware from its advertising network, after malicious code there had gone undetected for at least six days.

Security researchers at Malwarebytes said they discovered malicious ads planted in Yahoo's network on Sunday and alerted Yahoo. The malware attack had been underway since last Tuesday, wrote Jerome Segura, a senior security researcher at Malwarebytes Labs.

The malware was found in Yahoo's ads network at ads.yahoo.com, which runs ads across Yahoo's sites like its finance, games and news portals, as well as Yahoo.com. Users may have come across the infected ads when visiting Yahoo's sites.

A Yahoo spokeswoman declined to say how many advertisers were affected.

The attack used a method known as malvertising, in which attackers dupe online publishers into running malicious ads. They look like any other ads and may not require any interaction from users to infect their machines. If a visitor comes across a malicious ad, it can cause their browser to redirect to another site that attacks their computer.

In Yahoo's case, Malwarebytes detected ransomware, which encrypts files on users' computers unless they pay money to the attackers. The malware had also targeted sites hosted by Microsoft's Azure cloud platform, Malwarebytes said.

It's not the first time Yahoo's system has been hit with malvertising. Last year, an aggressive campaign was discovered that affected visitors across Yahoo and AOL's sites.

Malvertising might be becoming more prevalent in general. Last week, security company Cyphort said 10 million people may have visited websites carrying malicious ads in the last 10 days alone.

Experts advise users to keep their operating systems, browsers and browser plug-ins up to date to avoid becoming infected by malvertising. Yahoo visitors can also run a scan with their antivirus or anti-malware software, Malwarebytes said.

Zach Miners covers social networking, search and general technology news for IDG News Service. Follow Zach on Twitter at @zachminers. Zach's e-mail address is zach_miners@idg.com

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags internetmalwareadvertisingYahooInternet-based applications and servicesMalwarebytes

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Zach Miners

IDG News Service
Show Comments

Cool Tech

Bang and Olufsen Beosound Stage - Dolby Atmos Soundbar

Learn more >

Toys for Boys

ASUS ROG, ACRONYM partner for Special Edition Zephyrus G14

Learn more >

Sony WF-1000XM3 Wireless Noise Cancelling Headphones

Learn more >

Nakamichi Delta 100 3-Way Hi Fi Speaker System

Learn more >

Family Friendly

Mario Kart Live: Home Circuit for Nintendo Switch

Learn more >

Philips Sonicare Diamond Clean 9000 Toothbrush

Learn more >

Stocking Stuffer

Teac 7 inch Swivel Screen Portable DVD Player

Learn more >

SunnyBunny Snowflakes 20 LED Solar Powered Fairy String

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Tom Pope

Dynabook Portégé X30L-G

Ultimately this laptop has achieved everything I would hope for in a laptop for work, while fitting that into a form factor and weight that is remarkable.

Tom Sellers

MSI P65

This smart laptop was enjoyable to use and great to work on – creating content was super simple.

Lolita Wang

MSI GT76

It really doesn’t get more “gaming laptop” than this.

Jack Jeffries

MSI GS75

As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr

MSI PS63

The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Featured Content

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?