Cellphone jammer detector ideas? - Page 1
Forum section: electronics / projects

author: ftransform
author_rank: Frequent Contributor
timestamp: October 22, 2012, 08:53:31 am
content: So with societies reliance on cellphones, and the possibility of jamming, is it possible to modify a cellphone via software to recognize a jamming signal or is it necessary to build special hardware?The old Nokia phone has been pretty well reverse engineered so I thought that it may provide a good base for a hardware based project. Perhaps it would be a simple system so that if there is a strong signal, but no connectivity, then alarm is raised. This would probably be the best because there are many many many different ways to jam radio. I am sure a jam signal could be made to look similar to a actual signal, making recognition very difficult.http://en.wikipedia.org/wiki/Nokia_3310This phone has been modified to serve as a spectrum analyzer of sorts.Of course you can look if connectivity is lost, but this can be a service issue, not necessarily enemy action.Post your ideas about cellphone jammer detection here.My crude idea is:Android loaded with program that checks for connectivity > IR transmitter loaded into the headphone jack (open source exists already) > IR REciever on board with a nokia 3310 "spectrum analyzer" monitoring frequencies of interest.The board would raise alarm if the connectivity signal indicated failure and the "spectrum analyzer" indicated the signal strength on the particular frequency was over the minimum connectivity thresh hold.I know I can actually set my android to display a dbm readout for signal strength but I don't know if thats a true measurement, so I don't know if one would need a external measurement.This is especially useful to all the people that do not have a landline anymore.

author: Rerouter
author_rank: Super Contributor
timestamp: October 22, 2012, 09:19:42 am
content: one thought would be to make use of the fact a tower in range would be transmitting intelligent data, so by partially decoding and testing that it fits the protocol, would cover all broadband noise jammers,the next would be that its very rare short of out in country for there to be only 1 tower in range, so you would check that there are more than 1 tower in range, an intelligent jammer would only act as 1,third tier would be to possibly use some echo command on the cellular network, i would assume even without a sim, one command or more would return a n_ack or even spoof an ID and see that it returns false, or possibly have a working set and see that it returns true,these methods i think would cover 95% of attacks, first for noise, second for intelligent jammer, third and forth for a rouge node attack, (doesnt jam but rather acts as a node that doesnt work)

author: ftransform
author_rank: Frequent Contributor
timestamp: October 22, 2012, 09:36:38 am
content: But then you would still need some kind of signal strength measurement because it could be a service interruption and there is no need to release the hounds.I liked your rogue node idea.Unless its a rogue node that transmits data to the real node but then stops when it wants to. That is a scary ass rogue node. How could we account for that one?Could the echo signal propagation delay be used to see if there is a new middle man in town?I wonder if the propagation delay for a echo signal is significantly greater if it has to go through 2 nodes or could it remain unnoticed due to the variable return time.

author: T4P
author_rank: Super Contributor
timestamp: October 29, 2012, 09:40:41 am
content: What could be tough but simple at the same time is judging the transmission power ... if you could.Pretty sure jammers can't output enough power to keep up with the massive towers but if you knew where the towers/panels were and the average power recieved, there's a slight chance you can bump into somebody holding some nondescript box with a weird antenna sticking out of it while hunting down the rogue tower"Satellite direction finders" are great for this, no need for a spec an but you could use a spec an if you wanted as you can see the spread of frequencies as well you can switch to a GSM band (Are there any GSM hackers nowadays or are they hacking GSM?) and see if there's a noticable increase unless you always knew there was something wrong in the HSDPA bandI might be talking rubbish but i thought i'll step in, this was the way i judged odd moments but in my country there are almost no towers, it's all just indoor and outdoor panels with massive satellite dishes (not sure about this, a entire football field? Maybe larger) pointing upwardsThe first time i was noticing something was odd with my signal and dropped calls i bumped into a jammer wazzock and gave him a good beating

author: croyleje
author_rank: Regular Contributor
timestamp: October 29, 2012, 02:15:46 pm
content: just my thoughts but unless you want to build something just for one particular type of phone [ie. GSM,CDMA,LTE,3G,4G, ect.] you would have to decode each one and check for intelligent data and connectivity and cellphone transmissions are extremely hard to decode i have seen some info on decoding the old GSM type phones online but not much. most of the commercially available and hacker built jammers use VCO's swept at around 20KHz across the frequency range. i think maybe looking for a large step in signal strength and also maybe looking for a rhythmic frequency sweep this would also cover all signal types easiest i think.just my thoughtsjason

author: Jacob
author_rank: Newbie
timestamp: November 16, 2012, 05:14:55 pm
content: If you are seeking for an choice to use a mobile cellphone jammer but different with the use of the product, you are in the right position. If you understand how to use the product in the right way, it can be very beneficial for you....

author: ptricks
author_rank: Frequent Contributor
timestamp: November 18, 2012, 01:25:13 pm
content: You can use the 'heartbeat' signal that is sent from towers to phones. It isn't part of the normal traffic so no data to decode. Each phone will keep sending replies until an acknowledge is received , once received the format changes to the tower sending 'are you here?" messages routinely and if a phone does not respond it removes that phone from its client list. The second part, the phone check from the tower is the part to check . The frequency used is fairly common among that carriers towers and isn't different for each phone in the area , they use the same frequency for the check and send the phones EIN in the packet so only that phone will reply.Some of the jammers target the heartbeat signal only because that is all that is needed to prevent the phone from working vs trying to jam the entire band.If the signal is present but the phone can't 'login' so to speak then you have a jammer being used.