Updated from 1:45 p.m. EDTSAN FRANCISCO -- Shares of authentication company Vasco Data Security ( VDSI) plunged Thursday after the authentication company missed analysts' expectations for the third quarter. Shares of Vasco closed down $13.43, or 33.9%, to $26.13 Thursday. The stock had touched it 52-week high of $44.25 last Wednesday. The company, which competes with EMC's ( EMC) security division RSA, makes hardware and software tokens that help businesses manage and control access to their networks, has seen its shares soar nearly 240% this year, mainly based on its robust outlook and its ability to beat quarterly expectations by a wide margin. Vasco's net income for the third quarter rose 79% to $5.9 million, or 15 cents a share, from $3.3 million, or 9 cents a share, in the year-ago quarter. Analysts had expected 17 cents a share. Revenue increased 60% to $30 million from $18.7 million a year ago. That missed analysts' expectations of $31.29 million. Third-quarter operating expenses, which included $600,000 worth of stock-based incentives, reached $11.7 million compared to $7.8 million in the same quarter a year ago. Vasco won 608 new customers in the third quarter, including 106 banks and 502 enterprise security customers. The failure to meet revenue expectations for the third-quarter revenue miss along with such "disappointing" indicators as the $33.4 million in backlog orders versus analyst estimates of $35 million and fewer-than-expected banks signed as customers could be signs of a slowdown in the business, says Robert Breza, an analyst with RBC Capital in his research note.