Security experts from Symantec are warning of tech support scams abusing Call Optimization Services to insert phone numbers.

Crooks are improving their tech support scams by using Call Optimization Services that are commonly used in legitimate call center operations to perform:

Tracking the source of inbound calls

Creation and management of phone numbers

Call load balancing

Call forwarding

Call analytics

Call routing

Call recording

Scammers continue to improve their techniques and now they are using the service to dynamically insert phone numbers into their scam web pages and potentially gain additional features to make their scams more successful

The scams begin when unaware victims visit a malicious website or are redirected to a bogus website in various ways such as a malvertising campaign.

“The scam web page informs the victim that the computer has been blocked due to a malware infection and tries to lure the user into calling a “toll free” number for assistance. An audio file, stating that the computer is infected, is also played in the background when the user arrives on the scam web page.” reads the analysis published by Symantec.

T he malicious page implements some tricks to avoid victims will close the page. The pages show display notification dialogs in full-screen mode or execute a javascript routine that makes the site unresponsive.

The pages display a list of numbers to call to fix the problem and users in panic tend to call them.

According to Symantec, crooks leverages call optimization services in order to dynamically insert phone numbers into a scam page.

This specific tech support scams not only is performing browser fingerprinting, it retrieves the browser version as well based in which crooks redirect victims to different scam pages.

Crooks used a script in the call optimization services to check a specific tag in the scam URL, then the script retrieves the scammer’s phone number from the service’s servers. When the servers return the scammer’s phone number, the tag triggers the “Callback” function that retrieves and displays the appropriate phone number for victims to call. If the tag from the call optimization service is not present in the scam URL, the phone number is retrieved by loading an XML file using the function loadXMLDoc() which is then displayed on the scam page.

The advantage of using the call optimization service’s tag in the URL is that it allows the scammers to dynamically insert phone numbers into their scam pages that are localized. “localized” to provide a different number based on the victim’s country.

Victims are shown a phone number that calls someone that speaks their language.

“However, by using the call optimization service’s tag in the URL the scammers can dynamically insert phone numbers into their scam pages,” continues Symantec.

“This can be useful, for example, if victims are based in multiple countries, as the victim can be shown a phone number that calls someone that speaks their language.”

Crooks can abuse Call Optimization Services in their tech support scams also for other goals, for example, to provide analytics, to implement load balancing during busy times to avoid losing calls.

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