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10/5/2018
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Successful Scammers Call After Lunch

Analysis of 20,000 voice phishing, or vishing, calls reveals patterns in how social engineers operate and how targets respond.

Voice phishing scams are most successful in the afternoon and least effective on Mondays, according to an analysis of thousands of these "vishing" calls over a three-year time frame.

Chris Hadnagy, founder and CEO of Social-Engineer, and Cat Murdock, a social engineer and pen tester at the company, had the idea to record vishing calls back in 2015. More than 20,000 calls later, they decided to compile the data they collected into a single report. Today, the duo took the stage today at DerbyCon to present their findings.

"Outside of malicious scam organizations, we may be one of the largest vishing centers in the world for social engineering professionals," said Hadnagy, in an interview with Dark Reading.

Of the 20,144 total calls made, 5,690 were completed, meaning the social engineer spoke with someone on the other end of the line. Of the completed calls, agents had a total of 3,017 compromises, a success ratio of 53%. Less than half (45.3%) of the calls resulted in a "shutdown," meaning they weren't able to get the minimum amount of data from their target.

Their calls dug up a total of 8,685 "flags," or pieces of information they had to obtain from their targets. This ranged from Social Security numbers, which they were able to learn 15.6% of the time, to information on internal projects (9.48%), to answers to security questions (1.1%).

Following are the key trends and takeaways from years of vishing data.

Mondays Are The Worst
An obvious statement, to be fair, but one that very much applies to vishing calls. Monday is the day you're most likely to get someone on the phone – but the least likely to compromise them.

"Monday is a really interesting outlier," Murdock said. The first day of the workweek has a compromise ratio of 29%, which is very low compared with Tuesday (62%), Wednesday (63%), Thursday (58%), and Friday (65%). People are most likely to answer the phone on Monday, which is also the day with the lowest voicemail ratio (60%) and shutdown ratio (70%).

Hadnagy, who admitted he doesn't know the targets' exact reasoning, put himself in their shoes.

"Monday, I just got back from the weekend, I'm refreshed, I'm ready to rock and roll," he said. "By the time Friday hits, I've been battered like an egg in a pan, and now I just wanna give up and go back to the weekend." What's more, he continued, people are more likely to take Fridays off for long weekends. Few folks take vacation on Mondays, so most people are in the office.

Drilling down into specific times of day, vishing calls are more successful the later it gets. Afternoon seems to be the best time, Murdock said, citing the 65% average compromise ratio.

When people arrive to their desks in the morning, the rate of compromise is lower. They're alert, they're focused, and they're less likely to share sensitive information. Later in the day, the compromise ratio increases, hitting its peak just as employees are getting ready to leave.

"Highest is at 5 p.m.," Murdock told Dark Reading. "People who are potentially working a little bit late and they're really ready [to leave, they'll] tell you what you need to get you off the phone."

Is That Call Really From HR?
The analysis also touched on the pretext, or the social engineer's strategy, for convincing their targets they were legitimate. More than three-quarters (76%) of agents pretended to work with facilities, 74% said they were calling as part of their work with a training department, 72% claimed to have lost the organization's address, and 63% pretended to be calling HR.

Impersonation, a tactic in which social engineers research a specific person and pretend to be that person to elicit information, is the most difficult technique to pull off, Murdock noted.

"It's one of our most challenging pretexts," she said. "You have to really know that person."

Hadnagy and Murdock divide the most common pretexts into two themes. One is HR, which encompasses vishing calls related to healthcare, databases, financial questions, open enrollment, portals, training, and wellness. The second was IT, where pretexts relate to audits, badges, databases, security, updates, and VoIP.

Yes, both categories include database-related questions. However, HR-related database calls had a higher compromise ratio (28%) than IT (21% compromise). Open enrollment vishing calls were the most effective, with a 100% compromise ratio. If you're looking to capture key data from HR, a well-timed open enrollment angle could be effective.

Women Are Winning
"Women just do better at social engineering," says Hadnagy, citing the data showing how female social engineers typically outperform males regardless of the target's gender.

This finding applies across all pretexts the team studied, meaning women were more successful in obtaining key information, whether they pretended to be an employee of the target company, a reporter, a facilities worker, IT personnel, or a training manager. The only area in which men were more effective than women was in calling with questions related to a conference.

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Black Hat Europe returns to London Dec 3-6 2018  with hands-on technical Trainings, cutting-edge Briefings, Arsenal open-source tool demonstrations, top-tier security solutions and service providers in the Business Hall. Click for information on the conference and to register.

Kelly Sheridan is the Staff Editor at Dark Reading, where she focuses on cybersecurity news and analysis. She is a business technology journalist who previously reported for InformationWeek, where she covered Microsoft, and Insurance & Technology, where she covered financial ... View Full Bio

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