Once known for its phones before losing out to Apple Inc iPhones and Android devices, BlackBerry now sells security software such as those used by corporations and government agencies. The company is also focusing on software used in emerging areas like driverless cars.

Adjusted revenue from BlackBerry's Internet of Things business, which includes the technology solutions and enterprise software and services (ESS) units, fell 5% to $134 million, missing estimates for the second straight quarter. Analysts on average had expected revenue of $150 million from the business.

The technology solutions segment, which houses QNX - a software used by carmakers to provide infotainment and other services to customers - continued to perform well with double-digit growth, but there was softness in the ESS business, Chief Executive Officer John Chen said on a post-earnings call.

Raymond James analysts estimated a revenue fall of 15% to 17% in the enterprise software segment.

"I would say that the weakness of ESS is really on execution," Chen said, attributing it to changes in its sales team.

The company said it now expects current-year revenue to rise between 23% and 25%, compared to its earlier forecast of 23%-27%.

In response to a question from an analyst about competition, Chen said the company saw Microsoft Corp being "a little bit more aggressive".

Waterloo, Ontario-based BlackBerry posted a net loss of $44 million in the second quarter ended Aug. 31, compared with a profit of $43 million a year earlier, as it invested heavily to integrate recently acquired Cylance.

In February, the company bought the California-based cybersecurity firm, whose software uses machine learning to preempt security breaches.

BlackBerry's operating expenses rose nearly 80% to $219 million in the quarter.

On a per share adjusted basis, the company broke even, in line with analysts' expectations.

Adjusted revenue rose about 22% to $261 million, missing estimates of $266 million, according to IBES data from Refinitiv.

BlackBerry's U.S.-listed shares fell to $6.08 and the Toronto stock dropped to C$8.06.

(Reporting by Debroop Roy and Arunima Kumar in Bengaluru; Editing by Maju Samuel)

By Debroop Roy and Arunima Kumar