Security experts from Cisco Talos have uncovered two recent sextortion scam campaigns that appear to leverage on the Necurs botnet infrastructure.

Experts from Cisco Talos analyzed the two campaigns, one of them began on August 30, the other on October 5, the researchers named them ‘Aaron Smith’ sextortion scams after the ‘From: header’ of the messages.

Attackers use data from numerous data breach to carry out their campaigns, it October researchers from the Cybaze ZLab spotted a scam campaign that was targeting some of its Italian customers, crooks leverage credentials in Breach Compilation archive.

Crooks use email addresses and cracked passwords obtained through phishing attacks and data breaches to send out scam emails to potential victims pretending to be in possession of videos showing them while watching explicit videos.

The scammer demands a payment in cryptocurrency for not sharing the video.

Cisco Talos experts reported that the Aaron Smith campaigns sent out a total of 233,236 sextortion emails from 137,606 unique IP addresses.

“Talos extracted all messages from these two sextortion campaigns that were received by SpamCop from Aug. 30, 2018 through Oct. 26, 2018 — 58 days’ worth of spam.” reads the analysis published by Talos.

“Every message sent as a part of these two sextortion campaigns contains a From: header matching one of the following two regular expressions:

From =~ /Aaron\d{3}Smith@yahoo\.jp/

From =~ /Aaron@Smith\d{3}\.edu/ “

In total, SpamCop received 233,236 sextortion emails related to these “Aaron Smith” sextortion campaigns. The messages were transmitted from 137,606 unique IP addresses. The vast majority of the sending IP addresses, 120,659 sender IPs (87.7 percent), sent two or fewer messages as a part of this campaign. “

Top countries sending sextortion emails include Vietnam (15.9 percent), Russia (15.7 percent), India (8.5 percent), Indonesia (4.9 percent) and Kazakhstan (4.7 percent). I

According to Talos, the number of distinct email addresses targeted in the campaigns was 15,826, each recipient receiving on average a 15 sextortion messages. In just one case, a recipient received 354 messages.

Each sextortion spam message includes a payment demand that randomly varies from $1,000 up to $7,000.

“These six different payment amounts appear with almost identical frequency across the entire set of emails, suggesting that there was no effort made on the part of the attackers to tailor their payment demands to individual victims.” continues Talos.

Researchers discovered that about 1,000 sending IP addresses used in the Aaron Smith campaigns were also involved in another sextortion campaign analyzed by experts from IBM X-Force in September and that leveraged the Necurs botnet too.

The campaigns allowed crooks to earn a total of 23.3653711 bitcoins (roughly $146,380.31), the bitcoins were distributed across 58,611 unique bitcoin wallet addresses.

Only 83 of these wallets had active balances, in some cases the wallets received payments smaller than $1,000, a circumstance that suggests they were used in other spam campaigns.

“Most anti-spam solutions will filter out obvious sextortion attempts like the ones we highlighted in this post. However, that is no silver bullet. When these kinds of spam campaigns make it into users’ email inboxes, many of them may not be educated enough to identify that it’s a scam designed to make them give away their bitcoins.” concludes Talos.

“Unfortunately, it is clear from the large amount of bitcoin these actors secured that there is still a long way to go in terms of educating potential victims.”

Further technical details and IoCs are included in the analysis published by Talos.

Pierluigi Paganini

( Security Affairs – sextortion, cybercrime)

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