A U.S. software developer lost his high-paying job when his employer inadvertently discovered that works turned in by the 'prized employee' for a considerable amount of time were all made in China.

According to reports by Net-Security.org, the employee, identified as Bob, was actually delivering excellent results in the past two years, with the HR department of the American infrastructure firm giving "him glowing performance reviews because he apparently wrote clean code and submitted it on time."

But unknowing to the company, Bob perpetrated a scam involving a firm in Shenyang, China, which did all the 'dirty works' required of Bob's estimated $US250,000 a year job.

A probe conducted by the firm's network provider, Verizon, has unmasked the scheme that the erring programmer had set up. He contracted the Chinese firm to farm out the bulk of job responsibilities and paid them $US50,000 each year.

The rest of the salary, Bob collected and he continued to report for work, apparently using his commendable attendance as pretext to cover for his real daytime activities.

What was Bob doing whiling away his 'productive hours'? According to Verizon's Andrew Valentine, Bob was so hooked into social media activities that he didn't mind feigning he was working by spending countless hours on Facebook, LinkedIn, Reddit, eBay and YouTube.

At the end of each day, he dutifully informed management of his 9-to5 accomplishment, looking forward to sustain the fun-time as far as possible.

His smooth operation, however, got derailed when the company detected of a suspect activity, strange accesses from China on its virtual private network (VPN). Fearing a possible malware attack from the country, Verizon was called into the picture.

"We received a request ... asking for our help in understanding some anomalous activity that they were witnessing in their VPN logs," Mr Valentine told Net-Security.org.

He noted that a VPN concentrator had been previously established to allow some of the company's most-trusted workers to perform their duties remotely. It turned out that one of the recipients of the privilege was Bob, being considered as "one of the company's most respected employees."

But a deeper look on Bob's workstation yielded damning evidences that belied the reputation he had built up. He saved on his work PC hundreds of invoices in PDF forms, proving his connection to the Chinese firm.

All along, Bob was producing results that impressed his company but he had to thank outsourcing for that feat.

"Evidence even suggested he had the same scam going across multiple companies in the area," Mr Valentine said.

"All told, it looked like he earned several hundred thousand dollars a year, and only had to pay the Chinese consulting firm about $50,000 annually," he added.