We all know that our cell phones constantly give our location away to our mobile network operators; that’s how they work. A group of researchers has figured out a way to fix that. “Pretty Good Phone Privacy” (PGPP) protects both user identity and user location using the existing cellular networks. It protects users from fake cell phone towers (IMSI-catchers) and surveillance by cell providers.
It’s a clever system. The players are the user, a traditional mobile network operator (MNO) like AT&T or Verizon, and a new mobile virtual network operator (MVNO). MVNOs aren’t new. They’re intermediaries like Cricket and Boost.
Here’s how it works:
- One-time setup: The user’s phone gets a new SIM from the MVNO. All MVNO SIMs are identical.
- Monthly: The user pays their bill to the MVNO (credit card or otherwise) and the phone gets anonymous authentication (using Chaum blind signatures) tokens for each time slice (e.g., hour) in the coming month.
- Ongoing: When the phone talks to a tower (run by the MNO), it sends a token for the current time slice. This is relayed to a MVNO backend server, which checks the Chaum blind signature of the token. If it’s valid, the MVNO tells the MNO that the user is authenticated, and the user receives a temporary random ID and an IP address. (Again, this is now MVNOs like Boost already work.)
- On demand: The user uses the phone normally.
The MNO doesn’t have to modify its system in any way. The PGPP MVNO implementation is in software. The user’s traffic is sent to the MVNO gateway and then out onto the Internet, potentially even using a VPN.
All connectivity is data connectivity in cell networks today. The user can choose to be data-only (e.g., use Signal for voice), or use the MVNO or a third party for VoIP service that will look just like normal telephony.
The group prototyped and tested everything with real phones in the lab. Their approach adds essentially zero latency, and doesn’t introduce any new bottlenecks, so it doesn’t have performance/scalability problems like most anonymity networks. The service could handle tens of millions of users on a single server, because it only has to do infrequent authentication, though for resilience you’d probably run more.
The paper is here.
Posted on January 15, 2021 at 6:36 AM •
Gizmodo is reporting that schools in the US are buying equipment to unlock cell phones from companies like Cellebrite:
Gizmodo has reviewed similar accounting documents from eight school districts, seven of which are in Texas, showing that administrators paid as much $11,582 for the controversial surveillance technology. Known as mobile device forensic tools (MDFTs), this type of tech is able to siphon text messages, photos, and application data from student’s devices. Together, the districts encompass hundreds of schools, potentially exposing hundreds of thousands of students to invasive cell phone searches.
The eighth district was in Los Angeles.
Posted on December 18, 2020 at 6:53 AM •
Gizmodo is reporting that Harris Corp. is no longer selling Stingray IMSI-catchers (and, presumably, its follow-on models Hailstorm and Crossbow) to local governments:
L3Harris Technologies, formerly known as the Harris Corporation, notified police agencies last year that it planned to discontinue sales of its surveillance boxes at the local level, according to government records. Additionally, the company would no longer offer access to software upgrades or replacement parts, effectively slapping an expiration date on boxes currently in use. Any advancements in cellular technology, such as the rollout of 5G networks in most major U.S. cities, would render them obsolete.
The article goes on to talk about replacement surveillance systems from the Canadian company Octasic.
Octasic’s Nyxcell V800 can target most modern phones while maintaining the ability to capture older GSM devices. Florida’s state police agency described the device, made for in-vehicle use, as capable of targeting eight frequency bands including GSM (2G), CDMA2000 (3G), and LTE (4G).
A 2018 patent assigned to Octasic claims that Nyxcell forces a connection with nearby mobile devices when its signal is stronger than the nearest legitimate cellular tower. Once connected, Nyxcell prompts devices to divulge information about its signal strength relative to nearby cell towers. These reported signal strengths (intra-frequency measurement reports) are then used to triangulate the position of a phone.
Octasic appears to lean heavily on the work of Indian engineers and scientists overseas. A self-published biography of the company notes that while the company is headquartered in Montreal, it has “R&D facilities in India,” as well as a “worldwide sales support network.” Nyxcell’s website, which is only a single page requesting contact information, does not mention Octasic by name. Gizmodo was, however, able to recover domain records identifying Octasic as the owner.
Posted on October 26, 2020 at 6:53 AM •
There is a new report on police decryption capabilities: specifically, mobile device forensic tools (MDFTs). Short summary: it’s not just the FBI that can do it.
This report documents the widespread adoption of MDFTs by law enforcement in the United States. Based on 110 public records requests to state and local law enforcement agencies across the country, our research documents more than 2,000 agencies that have purchased these tools, in all 50 states and the District of Columbia. We found that state and local law enforcement agencies have performed hundreds of thousands of cellphone extractions since 2015, often without a warrant. To our knowledge, this is the first time that such records have been widely disclosed.
Lots of details in the report. And in this news article:
At least 49 of the 50 largest U.S. police departments have the tools, according to the records, as do the police and sheriffs in small towns and counties across the country, including Buckeye, Ariz.; Shaker Heights, Ohio; and Walla Walla, Wash. And local law enforcement agencies that don’t have such tools can often send a locked phone to a state or federal crime lab that does.
The tools mostly come from Grayshift, an Atlanta company co-founded by a former Apple engineer, and Cellebrite, an Israeli unit of Japan’s Sun Corporation. Their flagship tools cost roughly $9,000 to $18,000, plus $3,500 to $15,000 in annual licensing fees, according to invoices obtained by Upturn.
Posted on October 23, 2020 at 8:47 AM •
The 5GBioShield sells for £339.60, and the description sounds like snake oil:
…its website, which describes it as a USB key that “provides protection for your home and family, thanks to the wearable holographic nano-layer catalyser, which can be worn or placed near to a smartphone or any other electrical, radiation or EMF [electromagnetic field] emitting device”.
“Through a process of quantum oscillation, the 5GBioShield USB key balances and re-harmonises the disturbing frequencies arising from the electric fog induced by devices, such as laptops, cordless phones, wi-fi, tablets, et cetera,” it adds.
Turns out that it’s just a regular USB stick.
Posted on May 29, 2020 at 12:02 PM •
Glenn Greenwald has been charged with cybercrimes in Brazil, stemming from publishing information and documents that were embarrassing to the government. The charges are that he actively helped the people who actually did the hacking:
Citing intercepted messages between Mr. Greenwald and the hackers, prosecutors say the journalist played a “clear role in facilitating the commission of a crime.”
For instance, prosecutors contend that Mr. Greenwald encouraged the hackers to delete archives that had already been shared with The Intercept Brasil, in order to cover their tracks.
Prosecutors also say that Mr. Greenwald was communicating with the hackers while they were actively monitoring private chats on Telegram, a messaging app. The complaint charged six other individuals, including four who were detained last year in connection with the cellphone hacking.
This isn’t new, or unique to Brazil. Last year, Julian Assange was charged by the US with doing essentially the same thing with Chelsea Manning:
The indictment alleges that in March 2010, Assange engaged in a conspiracy with Chelsea Manning, a former intelligence analyst in the U.S. Army, to assist Manning in cracking a password stored on U.S. Department of Defense computers connected to the Secret Internet Protocol Network (SIPRNet), a U.S. government network used for classified documents and communications. Manning, who had access to the computers in connection with her duties as an intelligence analyst, was using the computers to download classified records to transmit to WikiLeaks. Cracking the password would have allowed Manning to log on to the computers under a username that did not belong to her. Such a deceptive measure would have made it more difficult for investigators to determine the source of the illegal disclosures.
During the conspiracy, Manning and Assange engaged in real-time discussions regarding Manning’s transmission of classified records to Assange. The discussions also reflect Assange actively encouraging Manning to provide more information. During an exchange, Manning told Assange that “after this upload, that’s all I really have got left.” To which Assange replied, “curious eyes never run dry in my experience.”
Good commentary on the Assange case here.
It’s too early for any commentary on the Greenwald case. Lots of news articles are essentially saying the same thing. I’ll post more news when there is some.
EDITED TO ADD (2/12): Marcy Wheeler compares the Greenwald case with the Assange case.
Posted on January 21, 2020 at 3:23 PM •
SIM hijacking — or SIM swapping — is an attack where a fraudster contacts your cell phone provider and convinces them to switch your account to a phone that they control. Since your smartphone often serves as a security measure or backup verification system, this allows the fraudster to take over other accounts of yours. Sometimes this involves people inside the phone companies.
Phone companies have added security measures since this attack became popular and public, but a new study (news article) shows that the measures aren’t helping:
We examined the authentication procedures used by five pre-paid wireless carriers when a customer attempted to change their SIM card. These procedures are an important line of defense against attackers who seek to hijack victims’ phone numbers by posing as the victim and calling the carrier to request that service be transferred to a SIM card the attacker possesses. We found that all five carriers used insecure authentication challenges that could be easily subverted by attackers.We also found that attackers generally only needed to target the most vulnerable authentication challenges, because the rest could be bypassed.
It’s a classic security vs. usability trade-off. The phone companies want to provide easy customer service for their legitimate customers, and that system is what’s being exploited by the SIM hijackers. Companies could make the fraud harder, but it would necessarily also make it harder for legitimate customers to modify their accounts.
Posted on January 21, 2020 at 6:30 AM •
SRLabs founder Karsten Nohl, a researcher with a track record of exposing security flaws in telephony systems, argues that RCS is in many ways no better than SS7, the decades-old phone system carriers still used for calling and texting, which has long been known to be vulnerable to interception and spoofing attacks. While using end-to-end encrypted internet-based tools like iMessage and WhatsApp obviates many of those of SS7 issues, Nohl says that flawed implementations of RCS make it not much safer than the SMS system it hopes to replace.
Posted on December 16, 2019 at 6:00 AM •
This wasn’t a small operation:
A Pakistani man bribed AT&T call-center employees to install malware and unauthorized hardware as part of a scheme to fraudulently unlock cell phones, according to the US Department of Justice. Muhammad Fahd, 34, was extradited from Hong Kong to the US on Friday and is being detained pending trial.
An indictment alleges that “Fahd recruited and paid AT&T insiders to use their computer credentials and access to disable AT&T’s proprietary locking software that prevented ineligible phones from being removed from AT&T’s network,” a DOJ announcement yesterday said. “The scheme resulted in millions of phones being removed from AT&T service and/or payment plans, costing the company millions of dollars. Fahd allegedly paid the insiders hundreds of thousands of dollars — paying one co-conspirator $428,500 over the five-year scheme.”
In all, AT&T insiders received more than $1 million in bribes from Fahd and his co-conspirators, who fraudulently unlocked more than 2 million cell phones, the government alleged. Three former AT&T customer service reps from a call center in Bothell, Washington, already pleaded guilty and agreed to pay the money back to AT&T.
Posted on August 8, 2019 at 6:22 AM •
I know there’s a lot of politics associated with this story, but concentrate on the cybersecurity aspect for a moment. The cell phones of a thousand Brazilians, including senior government officials, were hacked — seemingly by actors much less sophisticated than rival governments.
Brazil’s federal police arrested four people for allegedly hacking 1,000 cellphones belonging to various government officials, including that of President Jair Bolsonaro.
Police detective João Vianey Xavier Filho said the group hacked into the messaging apps of around 1,000 different cellphone numbers, but provided little additional information at a news conference in Brasilia on Wednesday. Cellphones used by Bolsonaro were among those attacked by the group, the justice ministry said in a statement on Thursday, adding that the president was informed of the security breach.
In the court order determining the arrest of the four suspects, Judge Vallisney de Souza Oliveira wrote that the hackers had accessed Moro’s Telegram messaging app, along with those of two judges and two federal police officers.
When I say that smartphone security equals national security, this is the kind of thing I am talking about.
Posted on August 7, 2019 at 10:48 AM •
Sidebar photo of Bruce Schneier by Joe MacInnis.