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How reliable is the tape evidence against Hubert Webb?


When the National Bureau of Investigation (NBI) presented its findings in the reinvestigation of the Vizconde massacre case on Tuesday, one electronic device figured prominently in the headlines: the magnetic reel tape that allegedly proved that the suspect, Hubert Webb, was in the country at the time of the murders. According to NBI Death Investigation Division head Romulo Asis, magnetic reel tape records from the Bureau of Immigration (BI) showed no log of Webb having ever left the Philippines in June 1991, although there was an entry that showed that he returned to the country in 1992. The tapes were presented in an effort to challenge Webb's defense that he was in the United States when the massacre happened — the alibi that got Webb acquitted last December, after spending 15 years in jail. First-generation devices In an interview with GMA News' News to Go on Wednesday, Engr. Jolly Bert Galeon, chief of the computer section of the BI said that the tapes —specifically IBM model AS/400 server tape drives— were primarily used by the agency to log records of individuals leaving and entering the country. "Yan po iyong makina na ginagamit po ng immigration, 'yan po ay mga first-generation na makina po. Actually, during the late 80's and early 90's, yan po yung ginagamit nila. Sa ngayon po, wala na ho kaming ginagamit na (ganyan)," he said. (Those are first-generation devices used by the immigration department. Actually, during the late 80's and early 90's, that's what they used. But as of now, nobody uses them anymore.) But how reliable are these tapes? And is there meat to the accusation that the tapes have already been tampered with? Tale of the tape According to Lito Averia, computer expert and president of the Philippine Computer Emergency Response Team, the nature of magnetic reel tape systems makes them very difficult to tamper with. Magnetic tape storage works on a similar principle to audio cassette tapes: information is stored in a continuous or "linear" stream of data across the full length of the tape. This makes it almost impossible to simply just cut out data from any section of the tape. In contrast, modern hard disks and compact disks store data in a "non-linear" manner, allowing users to quickly delete files without touching other adjacent files. "For you to tamper with the data inside the tape (without leaving a trace), you would have to upload it to a hard disk first, tamper with the data, then create another backup tape. You would also have to know how the data is written, the format of the data, and length of the record that you would like to remove," explained Averia. Simple explanation However, Averia added that there may be a simple explanation as to why the tapes contain no record of Webb's departure: it may have just been a matter of human error. He explained that, back in the day, data was not recorded directly into the database when someone exited or entered the country. One would have to fill up a disembarkation form first, and this is what the BI would use to enter the information manually into the computer. "(The disembarkation card) could have easily gotten lost somewhere, or somebody missed entering it into the database," Averia said. Security measures and audit trails However, Galeon that it would still be very difficult for this to happen, because of the BI's security measures. He explained that the tapes are stored in a secure server room, and strict auditing procedures are employed to keep track of everyone who has access to them. "Napakahirap pong gawin yon (tampering). Meron rin pong mga audit trails 'yan (pero) hindi ko lang ho alam kung paano nila pinaiiral 'yung mga security features noong araw.," he said. (It's very difficult to tamper with them. There are audit trails, but I'm not sure how the security features were implemented back then.) Tapes restored for analysis Galeon admitted that, since the IBM model AS/400 is already phased-out from use by the department, the BI does not have the capability to directly examine the data on the tapes. NBI's Asis said that the tapes were restored by technology company IBM while being monitored by the National Computer Center. For its part, IBM Philippines told GMA News in an SMS message that it was not involved in the analysis of the tapes. "IBM, as the manufacturer of the AS/400 server, was (only) engaged by the NBI to help source for an AS/400 machine to enable them to read the magnetic reel tapes," the company explained. — GMA News

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