L0pht Heavy Industries (pronounced "loft") was a hacker collective active between 1992 and 2000 and located in the Boston , Massachusetts area. The L0pht was one of the first viable hackerspaces in the US, and a pioneer of responsible disclosure . The group famously testified in front of Congress in 1998 on the topic of ‘Weak Computer Security in Government’.
51-567: The second character in its name was originally a slashed zero , a symbol used by old teletypewriters and some character mode operating systems to mean zero. Its modern online name, including its domain name , is therefore "l0pht" (with a zero, not a letter O or Ø ). The origin of the L0pht can be traced to Brian Oblivion and Count Zero, two of the founding members, sharing a common loft space in South Boston with their wives (Mary and Alicia) who ran
102-686: A binary BCH code (31, 21). The error-correcting code has a 6-bit Hamming distance : each 31-bit codeword differs from every other codeword in at least 6 bits. Consequently, the code can detect and correct up to 2 errors in a codeword. The generating polynomial g ( x ) for the BCH (31, 21) code is: The codewords are either address or data, which is indicated by the first bit transmitted, bit 31. An address codeword contains 18 bits of address (bit 30 through to 13), and 2 function bits (12 & 11). Each data codeword carries 20 bits of data (bits 30 through to 11). Codewords are transmitted in batches that consist of
153-540: A combining sequence. see Combining solidus below. Unicode 9.0 introduced another method to create a short diagonal stroked form by adding the Variation Selector 1 U+FE00 after the zero, on this browser it produces 0︀ . In most typographic designs, the slash of a slashed zero usually does not extend past the ellipse. Compare this to the Scandinavian vowel " Ø ", the " empty set " symbol "∅" and
204-483: A heavy metal umlaut Scandinavian vowel ø in the band's name and as the band logo on all their album covers (see link below). Along with the Westminster , MICR , and OCR-A fonts, the slashed zero became one of the things associated with hacker culture in the 1980s. Some cartoons depicted computer users talking in binary code with 1s and 0s using a slashed zero for the 0. Slashed zeroes have been used in
255-414: A font whose designer chose the option is active. Successful display on a particular local system depends on making sure that such a font is available there, either via the system's font files or via font embedding , and also ensuring it is selected. As an explicit visual representation, Unicode supports slashed zero only indirectly, not as a single-character code point , but as two characters are paired in
306-452: A hat business in one half of the space and helped to establish an IRL communal work space. There they experimented with their own personal computers, equipment purchased from the Flea at MIT , and items obtained from dumpster diving local places of interest. Founded in 1992 the L0pht quickly became a location for its members to store their computer hardware and work on various projects. In time,
357-619: A mixture of paging and land mobile communications. The VHF low band (35/43 MHz) frequencies are mainly used for local hospital paging and in many areas are completely unused. Australia uses the following frequencies for localised paging, such as in hospitals, hotels and other facilities, and also as an Emergency communication system for fire services (such as the Victorian Country Fire Authority ) and for ambulances. Other paging systems for wide-area paging, such as commercial networks are licensed and operate anywhere in
408-480: A slashed zero. It is used in many Baudot teleprinter applications, specifically the keytop and typepallet that combines "P" and slashed zero. Additionally, the slashed zero is used in many ASCII graphic sets descended from the default typewheel on the Teletype Model 33 . The use of the slashed zero by many computer systems of the 1970s and 1980s inspired the 1980s space rock band Underground Zerø to use
459-410: A space with a hat-making business run by the spouses of Brian Oblivion and Count Zero, and the rental cost was divided amongst them both. This was soon subsidized by profits made from selling old hardware at the monthly MIT electronic flea market during the summer. Occasionally, shell accounts were offered for low cost on the L0pht.com server to selected individuals; while these individuals had access to
510-423: A symptom. Slashed zeros are used on New Zealand number plates . The slashed zero predates computers, and is known to have been used in the twelfth and thirteenth centuries. In the days of the typewriter , there was no key for the slashed zero. Typists could generate it by first typing either an uppercase "O" or a zero and then backspace , followed by typing the slash key. The result would look very much like
561-423: A sync codeword, defined in the standard as 0x7CD215D8, followed by 16 payload codewords that are either address or data. Any unused codewords are filled with the idle value of 0x7A89C197. Although the address (also referred to as a RIC - Radio Identity Code or CAP code - Channel Access Protocol code) is transmitted as 18 bits the actual address is 21-bits long: the remaining three bits are derived from which of
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#1732875978542612-536: A white "S" within the black borders of the zero. In the FE-Schrift typeface, used on German car license plates , the zero is rectangular and has an "insinuated" slash: a diagonal crack just beneath the top right curve. Typefaces commonly found on personal computers that use the slashed zero include: Dotted zero typefaces: The zero with a dot in the center seems to have originated as an option on IBM 3270 display controllers. The dotted zero may appear similar to
663-409: Is frequency-shift keying (FSK) with a ±4.5 kHz shift on the carrier. The high frequency represents a 0 and the low frequency a 1. The ±4.5 kHz frequency shift is used along with a 25 kHz channel spacing, known as "wideband". Some jurisdictions require that all systems move to a "narrowband" configuration, using 12.5 kHz channels and ±2.5 kHz frequency shifts (for example,
714-570: Is a slightly increased error-correcting code reliability for messages that span more than one POCSAG packet. Within a codeword 7-bit characters are packed from left to right ( MSB to LSB ). The LSB of an ASCII character is sent first (is the MSB in the codeword) as per standard ASCII transmission conventions, so viewed as bits inside a codeword the characters are bit reversed. In the UK , most pager transmissions are in five bands at The frequency 466.075 MHz
765-630: Is an asynchronous protocol used to transmit data to pagers . Its usual designation is an acronym of the P ost O ffice C ode S tandardisation A dvisory G roup, the name of the group that developed the code under the chairmanship of the British Post Office that used to operate most telecommunications in Britain before privatization. Before the development and adoption of the POCSAG code, pagers used one of several codes such as binary Golay code . In
816-430: Is commonly referred to as 'alpha-paging', and 4-bit BCD is commonly referred to as 'numeric-paging'. BCD encoding packs 4 bit BCD symbols 5 to a codeword into bits 30-11. The most significant nibble (bits 30,29,28,27) is the leftmost (or most significant) of a BCD coded numeric datum. Values beyond 9 in each nibble (i.e. 0xA through 0xF) are encoded as follows: BCD messages are space padded with trailing 0xC's to fill
867-453: Is considered a typographic variation of the Arabic digit zero 0 , which is code point U+0030 . Since nearly all software requires each base-10 digit to have only a single, unique semantic representation, Unicode defines no code point (other than U+0030 ) for altering the visual appearance of zero. This means that the slashed zero glyph is displayed for U+0030 only— and then always —when
918-454: Is encoded as POCSAG and broadcast on these frequencies: In Switzerland the following frequencies are used: The Belgium POCSAG is used for paging over the A.S.T.R.I.D. network: In Italy , the 26.225-26.935 MHz band (AM/FM, odd frequency steps) and 40.0125-40.0875 MHz (in 25 kHz steps) may be used for local pagers. These frequencies are often used for on-site hospital paging systems, including voice paging. Use of POCSAG on
969-747: The Congress of the United States that they could shut down the entire Internet in 30 minutes. The Washington Post referred to the response as "a tragedy of missed opportunity". Four members of the original group Space Rogue, Weld Pond, Kingpin and Mudge held a briefing entitled "“A Disaster Foretold — And Ignored” Revisiting the First-Ever Congressional Cybersecurity Hearing" hosted by the Congressional Internet Caucus Academy. The briefing, held on May 22, 2018,
1020-513: The Flash-based artwork of Young-Hae Chang Heavy Industries , notably in their 2003 work, Operation Nukorea . The reason for their use is unknown, but has been conjectured to be related to themes of "negation, erasure, and absence". The slashed zero has the disadvantage that it can be confused with several other symbols. See the disambiguation page for the symbol Ø for a comprehensive listing: Ø (disambiguation) . In Unicode , slashed zero
1071-508: The Greek letter theta (particularly capital theta, Θ), but the two have different glyphs . In raster fonts, the theta usually has a horizontal line connecting, or nearly touching, the sides of an O; while the dotted zero simply has a dot in the middle. However, on a low-definition display, such a form can be confused with a numeral 8. In some fonts the IPA letter for a bilabial click (ʘ) looks similar to
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#17328759785421122-430: The U.S. Federal Communications Commission (FCC) has mandated this transition be completed prior to 2013.). Often single transmission channels contain blocks of data at more than one of the rates. Transmission uses 32-bit blocks called codewords. Each codeword carries 21 bits of information (bits 31 through 11), 10 bits of error-correcting code (bits 10 through 1), and an even parity bit (bit 0). Bits 31 through 1 are
1173-485: The "long solidus", which may be written in HTML as 0̸ , appears as 0̸ . Using the "short solidus overlay" U+0337 after a standard zero character is coded as 0̷ and produces the following: 0̷ . Some Burroughs / Unisys equipment displays a zero with a reversed slash, similar to the no symbol , 🛇 . POCSAG Radio-paging code No. 1 (usually and hereafter called POCSAG )
1224-466: The 1990s new paging codes were developed that offered higher data transmission rates and other advanced features such as European and network roaming . The POCSAG code originally transmitted at 512 bits per second. Faster transmission at 1200 or 2400 bits per second using so-called Super-POCSAG has mostly displaced the POCSAG in the developed world but the transition is still in progress. In 1976 an international group of engineers began to meet to explore
1275-683: The 26 MHz and 27 MHz band has been logged by several listeners in Europe, specifically frequencies 26.350 MHz, 26.500 MHz, 26.705 MHz, 26.725 MHz, 26.755 MHz, 27.005 MHz, 27.007 MHz, 27.255 MHz (see note below regarding legal use of 27.255 MHz for paging in the United States). It appears that US-specification paging systems operating on 27.255 MHz have been sold in Italy and other European countries. The former monopoly operator SIP (which later became TIM) used
1326-441: The 450-470 MHz band (plus 421-430 or 470-512 MHz in certain cities). In larger metropolitan areas with congested frequency spectrum, paging services will often share the same frequency as land mobile stations, or operate on an adjacent channel. For example, a department store may operate handheld walkie-talkies on 462.7625 MHz while there are high power pager transmitters on 462.7500 MHz and/or 462.7750 MHz in
1377-427: The 8 pairs of codewords in the batch the address is sent in. This strategy allows the receiver to turn off for a considerable percentage of the time as it only needs to listen to the pair that applies to it, thus saving a significant amount of battery power. Before a burst of data there will always be a preamble of at least 576 bits of data containing alternating 1s and 0s, allowing the receiver to synchronize itself to
1428-550: The L0pht.com server they were not members of L0pht. One of the first physical products sold for profit by L0pht was a POCSAG decoder kit, which was sold in both kit and assembled form. Subsequently, the Whacked Mac Archives were transferred to CD-ROM for sale, soon followed by CD copies of the Black Crawling System Archives. The command line version of L0phtCrack , the password cracker for Windows NT ,
1479-630: The National Security Agency, Glenn S. Gerstell quoted testimony from the L0pht’s hearing during his keynote to American Bar Association ’s 28th Annual Review of the Field of National Security Law Conference on November 1, 2018. As L0pht occupied a physical space, it had real expenses such as electricity, phone, Internet access, and rent. Early in the L0pht's history these costs were evenly divided among L0pht members. In fact, L0pht originally shared
1530-586: The Puck Building in New York City. In October 1999 L0pht was featured in a lengthy article in the New York Times Sunday Magazine . In the article Jeffrey Hunker , NSC's then Director of Information Protection, said about L0pht, "Their objective is basically to help improve the state of the art in security and to be a gadfly, so to speak." In January 2000, L0pht Heavy Industries merged with
1581-410: The character was later typed on a card punch . The slashed zero is used in a number of fields in order to avoid confusion with the letter "O". It is used by computer programmers , in recording amateur radio call signs and in military radio, as logs of such contacts tend to contain both letters and numerals. The slashed zero was used on teleprinter circuits for weather applications. In this usage it
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1632-442: The codeword. There is no POCSAG specified restriction on message length, but particular pagers of course have a fixed number of characters in their display. Alphanumeric messages are encoded in 7-bit ASCII characters packed into the 20 bit data area of a message codeword (bits 30-11). Since three seven bit characters are 21 rather than 20 bits and the designers of the standard did not want to waste transmission time, they chose to pack
1683-469: The diameter symbol ⌀ . A convention common on early line printers left zero unornamented but added a tail or hook to the letter-O so that it resembled an inverted Q (like U+213A ℺ ) or cursive capital letter-O ( O {\displaystyle \,{\mathcal {O}}\,} ). In the Fixedsys typeface, the numeral 0 has two internal barbs along the lines of the slash. This appears much like
1734-514: The digit "zero" ("0") from the Latin script letter " O " anywhere that the distinction needs emphasis, particularly in encoding systems, scientific and engineering applications, computer programming (such as software development ), and telecommunications. It thus helps to differentiate characters that would otherwise be homoglyphs . It was commonly used during the punch card era, when programs were typically written out by hand, to avoid ambiguity when
1785-555: The dotted zero. Alternatively, the dot can become a vertical trace, for example by adding a "combining short vertical line overlay" (U+20D3) . It may be coded as 0⃓ giving 0⃓ . Dotted zero is used on Slovak license plates since 2023. IBM (and a few other early mainframe makers) used a convention in which the letter O had a slash and the digit 0 did not. This is even more problematic for Danes , Faroese , and Norwegians because it means two of their letters—the O and slashed O ( Ø )—are visually similar. This
1836-420: The first 20 bits of an ASCII message into the first code word, the next 20 bits of a message into the next codeword and so forth. What this means that a 7-bit ASCII character of a message that falls on a boundary can and will be split between two code words, and that the alignment of character boundaries in a particular alpha message code word depends on which code word it is of a message. The side benefit of this
1887-556: The following frequencies for their pager service, called Teledrin: In France , POCSAG is operated by E*Message over the AlphaPage network on the 466 MHz frequency: In addition to the bands listed above, paging may be authorized on any frequency in the land mobile bands authorized under Part 90 of the FCC rules, including frequencies in the 72-76 MHz band as well as the usual 30.56-49.58 MHz, 150.775-162.000 MHz VHF bands and
1938-400: The installment sale loan. L0phtCrack has now been released as open source. Space Rogue had also published a book on February 24, 2023. L0pht membership varied but included at various times: Slashed zero The dotted or slashed zero 0̷ is a representation of the Arabic digit " 0 " (zero) with a slash or a dot through it. This variant zero glyph is often used to distinguish
1989-610: The members of L0pht quit their day jobs to start a business venture named L0pht Heavy Industries, a hacker think tank . The business released numerous security advisories. They also produced widely used software tools such as L0phtCrack , a password cracker for Windows NT , a POCSAG decoder, and CD software collections. In 1997, on August 8–10, Mudge , Brian Oblivion, Kingpin, Space Rogue, Stefan, Weld Pond, and John Tan of L0pht discussed recent projects and accomplishments, Windows NT, new projects, emerging trends and shortcomings in technologies, with Q&A session at Beyond HOPE at
2040-626: The possibility of developing a new code for wide area paging; paging networks covering regions of entire countries. These meetings were successful and in February 1981 the CCIR (Comité consultatif international pour la radio) the forerunner of the ITU-R accepted the code as Radiopaging Code No.1 (RPC No.1),(Rec, 584). The meetings were chaired by R.H.Tridgell and were attended by representatives of British, European, and Japanese pager manufacturers The modulation used
2091-406: The preceding character to create a composite glyph. This can be used to obtain a crude typographic approximation where the slash is contained within the zero. It is treated literally as "a zero that is slashed", and it is coded as two characters: a standard zero 0 followed by either "combining short solidus overlay" U+0337 or "combining long solidus overlay" U+0338 . For example, placing
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2142-572: The same city. Or, a restaurant will use 467.7500 MHz to alert customers when their table is ready (using so-called "coaster pagers") while a department store nearby uses 467.7500 MHz for their in-store communications. In both of these examples, the department store is forced to use a squelch system such as CTCSS or DCS . In many areas in the United States, these frequencies are used for land mobile (two-way) radio communications services in addition to paging. The VHF (152/157-158 MHz) and UHF (454/459 MHz) frequencies are often used for
2193-530: The signal, and is another mechanism that enables the receiver to be turned off for a large percentage of the time. A message will start with an address codeword followed by a number of data codewords and will continue until another address, a sync, or an idle codeword is sent. When the data bits are extracted they will be in one of two formats. There are two message coding formats for the data messages. Numeric messages are sent as 4 bit BCD values, and alphanumeric messages are sent as 7-bit ASCII . The 7-bit ASCII
2244-429: The startup @stake , completing the L0pht's slow transition from an underground organization into a " whitehat " computer security company. Symantec announced its acquisition of @stake on September 16, 2004, and completed the transaction on October 8 of that year. In March 2006, Weld Pond and Dildog founded application security company Veracode as a spin out from Symantec. The Veracode static binary analysis technology
2295-557: Was almost exactly 20 years after the original testimony and was streamed live via Facebook. At the Defcon 26 hacking conference, held on August 10, 2018 in Las Vegas, seven of the L0pht members sat on a panel entitled "The L0pht Testimony, 20 Years Later (and Other Things You Were Afraid to Ask)". Among other things the panel encouraged attendees to keep on hacking but stay on the side of the law that kept them out of jail. The General Counsel of
2346-450: Was built at @stake, based on prototypes and ideas incubated at the L0pht. On March 14, 2008, several members of L0pht sat at a panel at a standing-room-only group of infosec professionals at SOURCE:Boston. Present were Weld Pond, John Tan, Mudge, Space Rogue, Silicosis and Dildog. On May 19, 1998, all seven members of L0pht (Brian Oblivion, Kingpin , Mudge , Space Rogue, Stefan Von Neumann, John Tan, Weld Pond ) famously testified before
2397-542: Was given away free, but the GUI version was sold as a commercial product. This was followed by the creation of the Hacker News Network website to host advertisements. However, even with these sources of income, L0pht barely broke even, and eventually began doing custom security coding for companies like NFR. In January 2009, L0phtCrack was acquired by the original authors Zatko, Wysopal, and Rioux from Symantec. L0phtCrack 6
2448-445: Was later flipped and most mainframe chain or band printers used the opposite convention (letter O printed as is, and digit zero printed with a slash Ø ). This was the de facto standard from 1970s to 1990s. However current use of network laser printers that use PC style fonts caused the demise of the slashed zero in most companies – only a few configured laser printers to use Ø . Unicode supports combining characters, which overlay
2499-406: Was previously used by Hutchison Paging, but the network was shut down in 2000. The frequency is still reserved for paging but is not used. In Germany , well known transmissions are at Licensed paging is possible in any other VHF/UHF bands. In Spain , nationwide service was provided by Telefónica Mensatel but the network was shut down in 2012. The Swedish pager network marketed as "Minicall"
2550-589: Was released at the SOURCE Boston Conference on March 11, 2009. L0phtCrack 6 contains support for 64-bit Windows platforms as well as upgraded rainbow tables support. On April 21, 2020 Terahash announced it had acquired L0phtCrack , details of the sale were not released. As of July 1, 2021, the L0phtCrack software is no longer owned by Terahash, LLC. It has been repossessed by the previous owners, formerly known as L0pht Holdings, LLC for Terahash defaulting on
2601-402: Was sometimes called communications zero. The slashed zero can be used in stoichiometry to avoid confusion with the symbol for oxygen (capital O). The slashed zero is also used in charting and documenting in the medical and healthcare fields to avoid confusion with the letter "O". It also denotes an absence of something (similar to the usage of an " empty set " character), such as a sign or
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