Ehud Tannenbaum, who used the computer hacker nom de guerre "The Analyzer," will begin to serve his 18-month sentence Tuesday, after the High Court rejected his appeal against the punishment meted out by the Tel Aviv District Court.

Tannenbaum, a 23-year-old Hod Hasharon resident, was convicted of offenses of conspiracy, wrongful infiltration of computerized material, disruption of computer use, and destroying evidence, after he, together with several other hackers, conspired in 1997 and early 1998 to commit various offenses via the Internet.

Tannenbaum obtained programs such as Trojan Horse, which facilitated illicit entry into classified computer systems; he also upgraded the programs. Tannenbaum admits that he used the Internet illegally to infiltrate computer systems operated by official American organizations, including the Defense Department, the Air Force and the Navy.

In rejecting Tannenbaum's appeal, justice Shlomo Levine wrote that, "the severity with which the sentencing court viewed the crimes leaves no room for a higher court to interfere with the sentence."