Data

I chose this week’s Question of the Week, saber tabatabaee yazdi‘s “Would publishing a network diagram make the network less secure?” because this is a point which seems to be often misunderstood.

Saber asked this question because he had come across various websites designed to let people share their network diagrams and designs in order that others can comment on them and provide guidance and he wondered what the risks would be from this.

As an example, this diagram from www.ratemynetworkdiagram.com provides IP addresses, host names and even descriptions:

AJ Henderson provided the very valid comment that security through obscurity is not security, but admits that any network will have some weaknesses, and avoiding giving this information to a potential attacker is probably advised.

My answer is taken from the experience of managing many hundreds of penetration tests. My take on it is:

having a map helps me target my attack, avoiding possible sensors, honeypots etc and aiming at high value targets or sources of information. This can speed up an attack immensely, reducing the defender’s chance of preventing it.

But the value from these sites is that you can have obvious mistakes pointed out to you – peer review can be a very valuable thing. So how can you do that safely?

To reduce risk, some steps you can take are:

• remove addresses, function titles etc
• only include sections of the network
• post under an anonymous profile
• include fake network sections

An attacker will still get information, but it hopefully won’t be enough to let them navigate your entire network.

Liked this question of the week? Interested in reading it or adding an answer? See the question in full. Have questions of a security nature of your own? Security expert and want to help others? Come and join us at security.stackexchange.com.

ZM15 asked this interesting question just before Christmas over on Superuser. It came over to Security Stack Exchange for some security specific input and I was delighted to see it, as I have done a fair bit of work in the practical elements of securing communications – so this blog post may be a tad biased towards my experiences.

For those not in the know, Powerline ethernet is a technology which allows you to transmit ethernet over your existing mains wiring – which is very useful for buildings which aren’t suitable for running cabling, as all you need to do is pop one of these where you want to connect a computer or other ethernet enabled device and they will be able to route TCP/IP packets. There are some caveats of course, the signal really only works on a single phase, so if you have multiple phases in your house the signal may not travel from one to another, although as DBasnett commented, to get around this, commercial properties may inject the signal deliberately onto all phases.

 Early Powerline adapters had very poor signal quality – noise on the mains caused many problems – but since then the technology has improved considerably, partly through increasing the signal strength, but also through improving the filters which allow you to separate signal from mains.

This is where the security problem lies – that signal can travel quite far down wires, and despite fuse boxes offering some resistance to signals, you can often find the signal is retrievable in the neighbour’s house. Damien answered:

I have experienced the signal bleed from my next door neighbor. I … could identify two other powerline adapters using the same network name. I got anywhere between 10 to 20Mbps of throughput between their adapters and mine. I was able to access their router, watch streaming video and see the computers on the network. I also noticed they had gotten IPs on my router also.

This prompted him to enable security.

Tylerl gave an excellent viewpoint, which is as accurate here as it has ever been:

Many of the more expensive network security disasters in IT have come from the assumption that “behind the firewall” everything is safe.

Here the assumption was that the perimeter of the house is a barrier, but it really isn’t.

Along even weirder lines, as is the way with any electrical signal, it will be transmitted to some degree from every wire that carries it, so if you have the right equipment you may be able to pick up the traffic from a vehicle parked on the street. This has long been an issue for organisations dealing in highly sensitive information, so various techniques have been developed to shield against these transmissions, however you are unlikely to have a Faraday cage built into your house. (See the article on TEMPEST over on Wikipedia or this 1972 NSA document for more information)

For similar wireless eavesdropping, read about keyboards, securing physical locations, this answer from Tom Leek and this one from Rook - all pointing out that to a determined attacker, there is not a lot the average person can do to protect themselves.

Scared yet?

Well, unless you have attackers specifically targeting you, you shouldn’t be, as it is very straightforward to enable security that would be appropriate for most individuals, at least for the foreseeable future. TEMPEST shielding should not be necessary and if you do run Powerline ethernet:

Most Powerline adapters have a security option – simply encryption using a shared key. It adds a little overhead to each communication, but as you can now get 1Gb adapters, this shouldn’t affect most of us. If you need >1Gb, get your property wired.

Liked this question of the week? Have questions of a security nature of your own? Security expert and want to help others? Come and join us at security.stackexchange.com.

Rather than focus on a specific question this week, we have 9 questions related to the destruction of data, 5 of which are specifically interested in destroying hard drives, as in this modern age where everything is recorded, there are good reasons for ensuring data is deleted when required.

So this post will concentrate on destroying the the drive itself. For the deletion of data from a storage device, have a look at our blog post for Question of the week number 4: How can you reliably wipe data from a storage device?

Matthew Doucette asked simply: How do you destroy an old hard drive?

To which Scott Pack produced the following incredibly detailed answer:

When it comes to drive destruction you typically see one of two main fields:

1. Disk Degaussing
2. Physical Destruction

Degaussing

Degaussing used to be the norm, but I am not such a big fan. On the plus side it is fast, you’ll normally just dump the disks on a conveyor belt and watch them get fed through the device. The problem is auditability. Since the circuitry is rendered wobbly, you won’t be able to do a spot check of the drives and verify that the data is gone. It is possible, with some level of probability unknown to me, that data could still exist on the platters. Retrieving the data would, without question, be difficult, but the fact still remains that you cannot demonstrate the data is actually gone. As such, most companies now will actually be doing physical destruction.

Physical Destruction

At the low end, say a small box of drives at a time, you’ll have hard drive crushers. They’re often pneumatic presses that deform the platters beyond useful recognition. At the risk of supporting a specific product, I have personally used this product from eDR. It works well, and is very cathartic.

At a larger scale, say dozens or hundreds of disks, you’ll find large industrial shredders. They operate just like a paper shredder, but are designed to process much stiffer equipment. The mangled bits of metal that are left over are barely identifiable as hard drives.

At an even larger scale you can start looking at incinerators that will melt the drives down to unidentifiable lumps of slag. Since most electronics can produce some rather scary fumes and airborne particulates, I would not recommend doing this on you own. No, this is not a good use of your chiminea.

Manual Dis-assembly

If you are dealing with one or two drives at a time, then simple dis-assembly might be sufficient. Most drives these days are largely held together with torx screws, and will come apart with varying levels of difficulty. Simply remove the top cover, remove the platters from the central spindle. Taking a pocket knife, nail file, screwdriver, whatever, have fun scoring both surfaces of each platter. Then dispose of the materials appropriately. I cannot speak to how recoverable the data is afterwards, but it is probably sufficient. The biggest thing to keep in mind is that while most desktop hard drive platters are metal, some are glass. The glass ones shatter quite extravagantly.

Additional Considerations

Before you decide on a destruction method, make sure to identify what kind of data is stored on each device and treat it appropriately. There may be regulatory or legal requirements for information disposal depending on what data is stored on the disk. As an example, see section 8-306 of DoD 5220.22-M.

For hard drive destruction, DoD 5220.22-M section 8-306 recommends: “Disintegrate, incinerate, pulverize, shred, or melt”

All that being said, performing a single pass zero wipe is probably sufficient for your purposes. Modern research indicates that modern hard drives are largely immune to the “magnetic memory” problem we used to see on magnetic tape. I would never bother doing anything more on a household drive unless the drive itself was exhibiting failures

Ryan M asked a very similar question - What is the best method of retiring hard drives?

And Scott also gave these 2 excellent points in his answer:

Electrical Scrambling

In the olden days when you had a room packed with tape there were few things better than a big honkin’degausser for making sure that you knew what left the room. As hard drives supplanted tape, their use simply got transferred to the new medium. The biggest advantage to using a degausser to take care of hard drives is speed. Just pass a box through the unit, ignore the jiggling in your fillings, and walk away with clean drives. The downside is the lack of ability to audit data destruction. As discussed in the Wikipedia article, once a hard drive is degaussed, the drive is mechanically unusable. As such, one cannot spot check the drive to ensure cleanliness. In theory the platters could be relocated to a new device and we cannot state, categorically, that the data will not be accessible.

Wanton Destruction

This is without question my favorite. Not only because we demonstrate, without question, that the data is gone, but the process is very cathartic. I have been known to take an hour or so, dip into the “To Be Destroyed” bin, and manually disassemble drives. For modern hard drives all you need is a torx set and time (possibly pliers). While one will stock up on their magnet collection, this method of destruction is very time consuming. Many companies have developed equipment specifically for hard drive destruction en-masse. These range from large industrial shredders to single unit crushers such as this beauty from eDR. I have personally used that particular crusher, and highly recommend it to any Information Security professional who has had a bit of a rough day.

I’m thinking if I ever need to destroy hard drives, I’ll either blow them up / give them to my kids / use them for target practice or ask Scott to have fun with them.

Dan Beale points out that exactly what approach you take depends on:

• how sensitive is the information
• how serious are the attackers
• do you need to follow a protocol
• do you need to persuade other people the data has gone

Auditability is essential if you are susceptible to regulations around data retention and destruction, and for most organisations this will be essential around regulations such as the Data Protection Act 1998 (UK), GLB or HIPAA (US) and others.