| Brian Vagnoni on 1 Oct 2007 05:32:21 -0000 |
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>From what I've been hearing 802.11 is going to be seriously supplanted by 802.16 in the WAN area. The messages I'm getting about the Philly MUNI 802.11 Wireless effort aren't good. For example: There is an Earthlink Philly MUNI access point on top of the light pole at 42nd and chester ave. We have an Earthlink USER access point mounted in an outdoor enclosure(ideal location) on the building at 4202 chester ave. This is a response from Tech Support I got recently: I have received word back from Earthlink regarding the coverage issues at 4202 Chester. Unfortunately, their answer doesn't help you much at the current time, but their comments about future plans may alleviate issues such as this from arising in the future. Earthlink's reply is below: ============== I have just heard back from our Net Engineering folks on this particular area - The reported back that this is a very marginal network connection area for us at this time and that would explain the poor connection Apple Vending is see at this time. Our Net Eng folks are working to improve the areas of the network with poor performance. They have identified this area and many others and are putting together a plan to address them. However, I can't give you a date for this particular area yet. We are also considering potentially removing marginal areas like this from our serviceability area in the short-term to reduce false positives seen by folks. ============== If this is a "marginal area" I'm really concerning about the future of the Philadelphia MUNI Wireless project. Sprint is rushing their XOhm 802.16e WiMAX into service which runs on 700MHz and has the ability for better building penetration than 802.11. One of the problems with the frequencies 802.11 uses other than it likes to bounce off solid objects rather than go through them is that there are only effectively 3 channels 1,6, & 11 for 802.11b backward compatibility. So ideally you would have you channel set to 6, your neighbors set to 1 and your other neighbor on the other side of the house set to 11. So that they don't interfere with one another. This is according to Cisco and what they recommend for stable 802.11 operation. Along with a minimum 35db SNR. In reality everything from cordless phones, wireless cameras, your car, computers and sat. radio all use the same set of frequencies. The spectrum is very, very crowded. I personally have a 2.4Ghz spectrum analyzer I use when I have interfere problems to see what is exactly on the spectrum. Another problem is that 802.11 was originally only designed as a LAN technology and is really not suited for WAN though people are trying make it work. With the use of external antennas, and amplifiers up to 1 watt of radiated power is allowed and some people claim to be able to get access to there systems up to and including a mile away. But again in a crowded spectrum problems still arise. Strong passwords are always a good idea but people have created WPA rainbow hash tables that speed up the process of brute force attacks greatly. In fact I'm downloading them as we speak. To give you an idea there are rainbow tables for windows, and rainbow crack makes the claim over a lan network that they can crack any windows password up to 14 characters in a matter of 30 minutes or less. See below: RainbowCrack is a general propose implementation of Philippe Oechslin's faster time-memory trade-off technique. In short, the RainbowCrack tool is a hash cracker. A traditional brute force cracker try all possible plaintexts one by one in cracking time. It is time consuming to break complex password in this way. The idea of time-memory trade-off is to do all cracking time computation in advance and store the result in files so called "rainbow table". It does take a long time to precompute the tables. But once the one time precomputation is finished, a time-memory trade-off cracker can be hundreds of times faster than a brute force cracker, with the help of precomputed tables. Some ready to work lanmanager and md5 tables are demonstrated in Rainbow Table section. One interesting stuff among them is the lm #6 table, with which we can break any windows password up to 14 characters in a few minutes. lm configuration #6
As far as Linux goes Ive personally been able to brute force crack Linux passwd files for an 8 character strong password in about 6 days on a 1.8GHz Dual Power MAC G5 with John the Ripper Pro v1.7.2; works about to about 2600 cps. If I had multi-threaded with defined character ranges even shorter. Brian I don't like talking about security stuff over public list if anyone wants to discuss this further we can do it in person at the meeting. See you Oct 3.
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