Russian hackers are using Twitter as an ultra-stealthy way of concealing their intrusions into sensitive Western government computer systems — a new surveillance technique that blends cutting edge digital engineering with old-fashioned spy tradecraft.

The hackers use images uploaded to the social media site to send messages and directions to malware — or malicious software — with which they have infected target computers.

The value of using Twitter as a means to control the malware — which may direct computers to steal files or other unintended operations — is that it is virtually invisible to most detection systems, appearing instead like myriad other visits users make to the social networking site.