Police are investigating charges against a former scientist with the ISRO and a software engineer for sending threatening e-mail to the Department of Atomic Energy. The scientist, Mr. I. S. Mudaliar, and the software engineer, Mr. Umang Dave, were arrested last month for hacking a web server belonging to Icenet, an Ahmedabad-based company, according to police sources. Mr. Mudaliar, who runs an Internet firm in Ahmedabad, had allegedly hacked different servers and panic- stricken users had turned to him for cybersecurity.