Category Archives: *nix

*nix, Hacking, Internet, Internet crime, Security

Blocking IP ranges at the router

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I’m sure that Russia is a wonderful place, and I’m sure that the vast majority of people there are lovely, and have no interest in harming anyone.

Sadly, from the perspective of a server operator, it sometimes feels that nothing good ever comes from Russia.

Being the diligent server operator that I (hopefully) am, I monitor things pretty closely. That includes network traffic coming from the Internet. Over the years, I’ve noticed that a huge proportion of the probes, DDoS attacks, spam, phishing, and hack attempts against my network come from IP addresses in Russia.

It’s gotten to the point where I am now actively blocking huge swathes of Internet addresses (IPs) that originate in Russia and neighbouring countries like the Ukraine.

Blocking those nasty IPs

I run a Linux web server, as well as several Internet-enabled services, at my home office. All of the communications between my server and the Internet pass through a router, making it the ideal place to block unwanted traffic for my entire network, which includes media computers, development systems, and the Windows computer on which I’m writing this.

I’m using a commercial router, but I’ve replaced the original firmware with Advanced Tomato. Doing this provides many benefits, including making it easier to manage the router’s firewall, IPTABLES. Here’s a typical IPTABLES command to block an IP address from the router’s Linux command line:
iptables -I FORWARD -s 185.219.52.90 -j DROP

The DROP directive tells the router to unceremoniously drop any traffic from the specified IP, without logging this action. Traffic can also be logged when it’s dropped, but excessive logging can cause performance problems and fill up logs with junk, so I just drop this traffic.

I issue commands like the one above at my router’s command line to block the traffic immediately, and then I update the router’s startup firewall script with the same command, so that it persists after the next router restart.

So there’s this one guy

There’s been one particularly persistent attacker in the last year or so. This person wants desperately to gain access to one of my Internet-accessible services, but he’s not particularly intelligent, because he keeps trying the same things over and over, in rapid succession. So much so, that at times the traffic he generates comes within shouting distance of a DDoS attack.

I started paying particular attention to traffic associated with a series of ports that are used by the service, and blocking the IP addresses at the other end of that traffic. Whereupon we embarked upon a long game of whac-a-mole, in which I blocked an IP or IP range, and the attacker moved to another host or VPN provider and resumed his attacks from there. It seems clear that this was all being done by one attacker, based on his quick reactions to my blocking.

This went on for several months, but now he appears to have given up. Or at least he’s moved on to other methods.

In the process of blocking all these IPs and networks, the attacker has also helpfully provided me with a list of VPN providers that should be blocked by, well, everyone. Everyone who doesn’t specifically need to allow them.

IP addresses and ranges I’m blocking

Almost all of these IPs and IP ranges are in Russia and the Ukraine. A few are elsewhere in Asia. Most of the ranges are VPN providers.
103.48.51.116
104.129.18.0/23
104.237.192.0/19
104.237.203.0/24
141.98.10.0/24
173.244.208.60
176.67.85.0/24
185.156.72.0/24
185.156.74.0/24
185.193.88.0/24
185.217.69.157
185.219.52.112
185.219.52.90
185.219.52.91
193.106.191.25
193.106.191.35
193.106.191.41
193.32.164.85
193.93.62.0/24
195.54.160.27
198.8.81.220
216.131.114.0/24
216.131.116.0/23
216.131.68.0/24
216.131.88.0/23
217.138.255.202
31.43.185.29
31.43.185.9
37.120.218.0/24
45.134.26.0/24
45.143.203.121
45.145.64.0/23
45.145.65.11
45.146.164.0/23
45.146.166.0/23
45.155.204.0/24
45.155.205.0/24
45.227.253.0/24
45.9.20.0/24
5.188.206.230
71.19.251.0/24
76.180.16.74
77.243.191.120
77.83.36.0/24
78.128.112.18
82.145.32.0/19
84.17.41.141
84.17.41.151
87.251.75.0/24
89.187.182.87
89.187.183.76
91.191.209.110
92.204.240.75
92.255.85.0/24
94.232.40.0/21
98.175.213.148

Here are a few other ranges I’m blocking for various reasons:

  • Hungarian ISP MAGYAR-TELEKOM-MAIN-AS IP range (unceasing garbage): 94.27.128.0/17
  • MediaLand BPH IP range (generally just horrible): 45.141.84.0/24
  • EE-GIGAHOSTINGSERVICES (constant email relay attempts): 176.111.173.0/24
*nix, Hardware, Linux, Mac, Patches and updates, Security, Things that are bad, Windows

Major slowdowns headed for almost all computers

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Major patches are coming, for most operating systems and devices running modern (made in the last 10 years or so) processors. Changes to Windows, Linux, macOS, and most other systems will modify the way memory is used, ameliorating critical CPU security flaws, and slowing them down significantly in the process.

There’s been a lot of secrecy around this issue, with details of the flaws — discovered several months ago — only now coming to light as O/S vendors scramble to prepare patches. The flaws (commonly referred to as Spectre and Meltdown) involve potential leaking of information, as described in a recent post on The Register:

At best, the vulnerability could be leveraged by malware and hackers to more easily exploit other security bugs.

At worst, the hole could be abused by programs and logged-in users to read the contents of the kernel’s memory. Suffice to say, this is not great. The kernel’s memory space is hidden from user processes and programs because it may contain all sorts of secrets, such as passwords, login keys, files cached from disk, and so on.

Much of this is still speculation, but the reality may be even worse, so hang onto your socks, since this is going to get ugly. It’s easy to imagine class action lawsuits arising out of the mess.

Those of you running light operating systems on older hardware may have the last laugh: while many of the world’s computers will soon be noticeably — and unavoidably — slower, yours will keep chugging along unaffected… at least until they’re used to access any of the millions of computers that power web sites and services. Major providers may have no choice but to install the updates, significantly reducing the processing power of their systems.

For computers running Windows 10, system updates are literally unavoidable, and the slowdown inevitable. The rest of us will need to decide whether to risk leaving the vulnerabilities exposed, or patch them and deal with the resulting performance hit. Exploiting the vulnerabilities is not straightforward, and it should be possible to stay safe by avoiding risky behaviour, such as indiscriminately running unknown software, visiting dubious web sites, and opening links in email. However, the full extent of the risks involved is not yet known.

Related articles

The Verge: Intel’s processors have a security bug and the fix could slow down PCs
The Verge: Microsoft issues emergency Windows update for processor security bugs
The Verge: Intel says processor bug isn’t unique to its chips and performance issues are ‘workload-dependent’
The Verge: Processor flaw exposes 20 years of devices to new attack
The Verge: How to protect your PC against the major ‘Meltdown’ CPU security flaw
Google Security Blog: Today’s CPU vulnerability: what you need to know
Bruce Schneier: Spectre and Meltdown Attacks
SANS InfoSec: Spectre and Meltdown: What You Need to Know Right Now
Techdirt: A Major Security Vulnerability Has Plagued ‘Nearly All’ Intel CPUs For Years

Update 2018Jan04: Corrected title and content to show that the problem affects all modern processors, not just those made by Intel, and that there are multiple vulnerabilities. Also added more related articles.

*nix, Adobe, Chrome, Flash, Internet, Internet Explorer, Malware, Mobile, Security, Spam and scams

July security roundup

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Flash improvements

Adobe is trying desperately to keep Flash viable. In July, they announced structural changes that are expected to strengthen Flash’s overall security. The changes are so far only available in the most recent versions of Chrome, but they are expected to find their way into the other major browsers in August.

Asprox botnet status

There’s an interesting (though technical) overview of recent changes in the behaviour of the Asprox botnet over on the SANS Handler’s Diary. Apparently the botnet is no longer sending malware attachments, and is instead sending pornography and diet-related spam. Comparing my inbox contents with the samples in the linked article, it looks like most of the spam I currently receive is thanks to Asprox. Hopefully Asprox will be targeted by the anti-botnet heavy hitters in the near future.

Flaw in BIND could cause widespread issues

BIND is one of the most common pieces of software on Internet-facing servers. It translates human-readable addresses like ‘boot13.com’ into IP addresses. A bug in version 9 of BIND causes it to crash when a specially-crafted packet is sent to it. Attackers could exploit this bug to execute an effective Denial of Service (DoS) attack against a server running BIND9. Patches have been created and distributed, but any remaining unpatched servers are likely to be identified and attacked in the coming months. Update 2015Aug05: As expected, this bug is now being actively exploited.

Mobile versions of IE are vulnerable

Current, patched versions of Internet Explorer running on mobile devices were recently reported to have four flaws that could allow attackers to run code remotely. Exploits were published, although none have yet been seen in the wild. The vulnerabilities were disclosed by the HP/TippingPoint researchers who discovered them, six months after they privately reported them to Microsoft. Microsoft has yet to patch these vulnerabilities; they apparently feel that vulnerabilities are too difficult to exploit for them to be dangerous.

Stagefright vulnerability on Android devices

A flaw in Stagefright, a core Android software library that processes certain types of media, makes almost all Android phones and tablets vulnerable. The flaw can be exploited as easily as sending a specially-crafted text (MMS) message to a phone, but also by tricking the user into visiting a specific web site. Successful attackers can then access user data and execute code remotely. Unfortunately for users, it’s up to individual manufacturers to develop and provide patches, and this process may take months in some cases. There’s not much users can do to mitigate this problem until patches arrive. Update 2015Aug05: Google is working with its partners to push updates to affected mobile devices.

Mediaserver vulnerability on Android devices

More bad news for Android users: the mediaserver service apparently has difficulty processing MKV media files, and can render a device unusable when it encounters one on a malicious web site. In most cases, the device can be brought back to life by powering it down and back up again.

Android spyware toolkit widely available

And the hits just keep on coming for Android devices. Among the information revealed in the recent Hacking Team breach was the source code for an advanced Android spyware toolkit called RCSAndroid. Like everything else taken from Hacking Team’s systems, this has now been published, and no doubt malicious persons are working on ways to use the toolkit. There’s no easy way to protect yourself from this toolkit, aside from keeping your device up to date with patches. From Trend Micro: “Mobile users are called on to be on top of this news and be on guard for signs of monitoring. Some indicators may come in the form of peculiar behavior such as unexpected rebooting, finding unfamiliar apps installed, or instant messaging apps suddenly freezing.”

*nix, Hardware, Internet, Internet crime, Linux, Malware, Mobile, Privacy, Security

Security roundup – May 2015

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Recent security breaches at mSpy and AdultFriendFinder are a gift for Internet extortionists. mSpy hasn’t helped matters by first denying the problem, and then trying to downplay its impact.

A serious vulnerability called Logjam has been discovered in the Diffie-Hellman Key Exchange software, which is used to secure communications on many web and email servers. Meanwhile, despite its many flaws, it’s still a good thing that the web is moving towards HTTPS encryption everywhere.

In the world of network-attached hardware, malware called Linux/Moose is exploiting vulnerabilities in routers and spreading across the Internet. A security flaw in NetUSB is making many consumer routers vulnerable.

A serious vulnerability in many virtual hardware platforms, including Oracle’s popular VirtualBox, is making life difficult for many service providers.

Those of you who monitor traffic arriving at your home or work network are no doubt aware that your network is being constantly scanned for vulnerabilities. Brian Krebs rightly points out that much of this scanning activity is not malicious.

And finally, before you exchange that Android device, you should know that even if you’ve performed a full reset, your personal data is not being completely erased.

*nix, Hardware, Internet, Linux, Mac, Patches and updates, Security

Shellshock: a very bad vulnerability in a very common *nix tool

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Linux and other flavours of the Unix operating system (aka *nix) run about half of the world’s web servers. Increasingly, *nix also runs on Internet-enabled hardware, including routers and modems. A huge proportion of these systems also have BASH configured as the default command interpreter (aka shell).

A serious vulnerability in BASH was recently discovered. The full extent of the danger related to this vulnerability has yet to be determined, because the bug opens up a world of possible exploits. As an example, the bug can be demonstrated by issuing a specially-crafted request to a vulnerable web server that results in that server pinging another computer.

Patches that address the vulnerability (at least partially) became available almost immediately for most Linux flavours. Apple’s OS X has yet to see a patch, but presumably that will change soon, although Apple has been oddly slow to respond to issues like this in the past.

Most average users don’t need to worry about this bug, but if you run a web server, or any server that’s accessible from the Internet, you should make sure your version of BASH is updated.

As new information emerges, I’ll post updates here.

References:

Update 2014Sep27: The first patch for BASH didn’t fix the problem completely, but another patch that does is now available for *nix systems. Still nothing from Apple for OS X. Scans show that there are thousands of vulnerable web servers on the Internet. Existing malware is being modified to take advantage of this new vulnerability. Attacks using the BASH vulnerability are already being observed. Posts from Ars Technica, Krebs on Security and SANS have additional details.

Update #2: It looks like there are more holes to be patched in BASH.

Update 2014Oct01: Apple releases a bash fix for OS X, more vulnerabilities are discovered, and either attacks based on bash vulnerabilities are increasing or attacks are subsiding, depending on who you ask.

Update 2014Oct08: Windows isn’t affected, unless you’re using Cygwin with bash. Oddly, Apple’s OS X bash patch is not available via the App Store; you have to obtain it from the main Apple downloads site. A security researcher claims to have found evidence of a new botnet that uses the Shellshock exploit.

Update 2014Oct23: Ars Technica: Fallout of Shellshock far from over