Right now, security professionals are scrambling to fix a security flaw some are calling Shellshock. It’s a major vulnerability related to Bash, a computer program that’s installed on millions of computers around the world. There’s been a lot of confusion in mainstream media accounts about how the bug works, who’s vulnerable, and what users can do about it.

In this explainer, I’ll first give a high-level explanation of who is vulnerable and what they can do about it. Then, for those who are interested, I’ll give a more technical explanation of exactly how the Bash bug works.

Who is vulnerable?

Bash (which we’ll discuss more below) is installed on many computers running operating systems derived from an ancient operating system called Unix. That includes Macs and iOS devices, as well as a lot of web servers running operating systems such as Linux.

Whether these computers are actually vulnerable depends on whether they invoke Bash in an unsafe way. We already know that this is true of many web servers, and it’s believed that other types of network services could also be vulnerable. But it’ll take a while for security experts to audit various pieces of software to check for vulnerabilities.

For the most part, consumer devices such as MacBooks and iPhones phones don’t seem to be running services that use Bash in an unsafe way. That means they are probably not vulnerable to hacks from across the internet. But we won’t know that for sure until security experts have had time for a careful audit.

Most Microsoft software doesn’t use Bash, so users running Windows PCs, people with Windows phones, as well as websites built using Microsoft software, are probably safe from these attacks. Also, it looks like most Android phones are not vulnerable because they use a Bash alternative.

What should I do to protect myself?

Unfortunately, there isn’t a ton you can do in the short run. Presumably, Apple will release updated versions of their software soon. So keep an eye out for that on your platform’s software update service, and install it as soon as it’s available.

There has also been some speculation that a service called DHCP might be vulnerable, though this is uncertain. This is a service that allows laptops, tablets, and smartphones to automatically configure themselves when they log into a wifi network. A malicious wifi router could use the bug to hack into users’ laptops and mobile devices. So if you’re a Mac or iPhone user, it might be prudent to avoid logging into untrusted wifi networks — for example, at coffee shops — until Apple has released a security update.

But for the most part, the vulnerability affects servers more than users’ own computers. So most of the heavy lifting needs to be done by security professionals, not the rest of us.

What could attackers do with this vulnerability?

The bug can be used to hack into vulnerable servers. Once inside, attackers could deface websites, steal user data, and engage in other forms of mischief.

There’s a good chance that hackers will use the vulnerability to create a worm that automatically spreads from vulnerable machine to vulnerable machine. The result would be a botnet, a network of thousands of compromised machines that operate under the control of a single hacker. These botnets — which are often created in the wake of major vulnerabilities — can be used to send spam, participate in denial-of-service attacks on websites or to steal confidential data.

As I write this, security professionals are racing to update their server software before the bad guys have time to attack it.

How hard will it be to fix the problem?

From a technical perspective, the fix shouldn’t be too difficult. A partial fix has already been made available, and a full fix should be released soon.

The tricky thing will be that, as with the Heartbleed vulnerability earlier this year, Bash is embedded in a huge number of different devices, and it will take a long time to find and fix them all.

For example, many home wifi routers run web servers to enable users to configure them using a web browser. Some of these devices may be vulnerable to a Bash-related attack. And unfortunately, these devices may not have an automatic or straightforward mechanism for upgrading their software. So old IT devices might have lingering vulnerabilities for many years.

OK, let’s get technical. What’s Bash?

Bash stands for Bourne-Again SHell. It’s a computer program that allows users to type commands and executes them. If you’re a Mac OS X user, you can check it out out yourself. Go to the Finder, open the Applications folder (from the “Go” menu), then the Utilities folder, and then open “Terminal.” It looks like this:

You can see in the menu bar that it says “bash,” indicating that the program running inside this terminal window is the Bash shell. The Bash shell understands a wide variety of commands. For example, “cd” stands for “change directory,” and tells the Bash shell to navigate to a new folder on your hard drive. Typing “ls” lists the contents of the current directory, while “echo” prints out text to the screen.

Bash has been around since the 1980s, and it has become an industry standard. To this day, it’s one of the most popular ways for systems administrators, computer programmers, and other tech-savvy users to execute complex commands on computers.

Because the Bash shell is entirely text-based, it’s particularly useful for administering a computer remotely. Running a Bash shell on a server halfway across the world feels exactly the same as running the Bash shell on your local computer. IT professionals use remote shells like Bash extensively to configure, diagnose, repair, and upgrade servers without having to physically travel to their location. As a result, Bash is a standard feature on almost all servers that run an operating system not made by Microsoft.

What’s the bug in Bash that people discovered this week?

Bash has a feature where users can set “environment variables” and retrieve them later. It works like this:

That’s a trivial example, but environment variables turn out to be an extremely useful feature when executing complex commands.

So what’s the bug? Here’s a slight variation on the previous example:

The “env” command sets an environment variable (in this case COLOR=red), and then executes a command based on that environment. Here, it’s executing a second Bash shell which in turn echoes the string “My favorite color is $COLOR.” Because the shell was running in an environment where COLOR=red, it prints out “My favorite color is red.”

The exploit works like this:

Notice that the command “echo I hate colors” doesn’t use the $COLOR variable at all. So if Bash were working correctly, the command “echo vulnerable” should be ignored — it’s just random text in a variable that never gets used. So the word “vulnerable” shouldn’t be in the output.

But the malicious string ‘() { :;}; echo vulnerable” takes advantage of a bug in the way Bash handles environment variables to trick it into treating the string “echo vulnerable” as a command rather than just a string of letters. Even worse, it does this automatically, even if it’s evaluating a command (like “echo I hate colors”) that doesn’t use the $COLOR variable at all!

Of course, in a real attack, the bad guys would do something a lot scarier than printing out the word “vulnerable.” They’d use this same mechanism to tell your computer to run spyware, send your private files to a remote server, send out spam, or do other bad stuff.

Wait, doesn’t an attacker need to have physical access to my computer to pull this off? That doesn’t sound very scary.

If Bash were only a mechanism for accepting commands from human users, this wouldn’t be such a big problem. The problem is that Bash has also become a popular way for computer programs to invoke other computer programs.

For example, when you load a website with dynamic content on it, the server handling the request may be using Bash commands to access the information you requested. So while most people never use Bash directly, we’re all using it constantly — indirectly — as we’re browsing the web.

Even worse, when a computer program uses Bash to invoke another computer program, it often uses environment variables to pass along user inputs. For example, when you visit a website, your browser sends the server a variable known as the “User Agent,” which tells the server something about which browser you’re running. (In my case, I’m running Chrome.)

Web servers often set this user-agent string as an environment variable before using Bash to execute code that generates the web page the user asked for. That allows the server to generate a different website for mobile and desktop browsers, for example.

But malicious parties can manually change their user-agent variable to contain, not a textual description of their browser, but a snippet of malicious code. And if they then visit a server that invokes a vulnerable version of Bash, the server will automatically execute this code, allowing the attacker to hack into the server.

Is anyone actually taking advantage of this bug?

Yes. Malicious software exploiting the vulnerability has already begun to appear online.

Correction: I originally stated that Android is vulnerable to the Bash vulnerability, but most Android phones ship with a competitor that, so far, does not appear to be vulnerable. I’ve updated the article accordingly. Also, I stated that a software patch to Bash would fix the problem, but it has since been discovered that the fix is incomplete.

Source: http://www.vox.com/2014/9/25/6843949/the-bash-bug-explained

A worrisome trend has been spotted recently of continuous DDoS attacks. After the Lizard Squad attack against Destiny and Call of Duty servers, the researchers confirmed a high volume of attacks that happened in the first six months of 2014. The players that suffered the attack were booted from the servers right in the middle of their game, when an error message occurred. The access to the game was restricted for several hours and the players complained about it, threatening to ask for their money back.

The trend of these DDoS attacks is likely to go on for two main reasons – the access to DDoS service solutions and the widespread coverage of the attacks. That is why the website operators need to put up defenses against the DDoS attacks.

DDoS attack duration

These attacks are short in duration and are repeated on a frequent basis. Approximately 90 % of the attacks that have been detected during that period of time lasted for less than half an hour. According to the experts, the ongoing trend is for attacks towards latency-sensitive websites including hosting service, online gaming and eCommerice. That is why these websites should apply different security solutions with rapid response.

DDoS attack strength
The attacks are of high rate and high volume. For example the DDoS traffic volume increased with one third reaching more than 500Mbps. Five percent of the DDoS traffic volume even reached up to 4Gbps. In the first half of 2014 more than 50% of the DDoS attacks were above 0.2Mpps, which is a 16 % increase. At the same time more than 2% of DDoS attacks were started at 3.2Mpps rate and above.

DDoS attack methods

DDoS attack methods
DDoS attacks are characterized with three main methods, namely DNS Flood, TCP Flood and HTTP Flood. The top three attack types form 85 % of all the attacks. The most popular method used are the DNS Flood attacks making 42 % of all the attacks noticed. The number of the HTTP Flood and the DNS Flood attacks has decreased, while at the same time the TCP Flood attacks grew substantially.

The ISPs attacks
The researchers found out that the number of the ISPs attacks has also increased by 87 %, the online gaming attacks increased by 60 % and the enterprises attacks increased by 100 %.

DDoS attacks of high-frequency

The DDoS attacks turned out to be one of the largest and longest, as well as the ones with highest frequency. The longest of all single attacks lasted for almost 12 days, while the largest single attack as far as packet-per-second was hit at 23 million pps volume.

At the same time, more than 40 % of the victims were targeted by the attack many times, and one in every 40 victims was hit repeatedly for more than 10 times. The highest frequency of attacks that has been noticed by one victim reached 68 separate DDoS attacks.

Source: http://sensorstechforum.com/ddos-attacks-gaming-sites/

The editorial Board of the Russia Today TV channel reported the most powerful DDoS attack on their website. This information was published on the website.

“Website RT.com today has been the most powerful DDoS attack for all time of existence of the channel. Power DDoS attack UDP flood on the RT site reached 10 Gbit/s. Thanks to the reliable technical protection of the site, RT.com was unavailable just a few minutes, however, the DDoS attack lasted”, – stated in the message.

Responsibility for hacker attack so far has not been declared.

Website RT.com subjected to DDoS attacks repeatedly. One of the most powerful hacker attacks occurred on February 18, 2013. The work of the RT site in English managed to recover only later, 6 hours after the start of the attack. In August 2012 sites of RT channels in English and Spanish were also under attack. Then the responsibility it has assumed hacker group AntiLeaks, which opposes the project WikiLeaks Julian Assange.

Source: http://newstwenty4seven.com/en/news/russia-today-zajavil-o-moschnejshej-ddos-atake-na-svoj-sajt

Question: What are botnets used for? Answer: Distributed Denial of Service (DDoS) Attacks.

Botnets are bad. The DDoS attacks that they can launch are even worse. The concept of a DDoS attack is simple. Generate enough malicious traffic to a web site, and it will become unable to respond to legitimate requests. In effect, the web site will be taken down. DDoS attacks have been used for retaliation, for political statements, for competitive reasons, and even for ransom.

The damage DDoS attacks can inflict on a company’s public-facing Internet services, such as web sites, or to the Internet in general is massive. There have been many examples of the use of botnets to bring major corporations to their knees:

  • In retaliation for the anti-Islamic YouTube video “Innocence of Muslims,” Islamic hackers launched massive DDoS attacks against several U.S. banks and took down their online banking portals for over a day each. Several months later, the hackers repeated their attacks; and they vowed to continue until the video is removed from the Internet. Their attacks so far have generated up to 70 gigabits per second (gbps) of malicious traffic – enough to overwhelm most web sites.
  • Spamhaus was hit with the most massive DDoS attack yet reported – a malicious data rate of 300 gbps! Spamhaus is a firm that maintains a blacklist of spam-generating sites and sells the list to corporations, government agencies, and ISPs so that they can block traffic from these sites. One of the web sites on the blacklist is CyberBunker, which advertises that it will post anything except child pornography and terrorist threats. It is CyberBunker that is suspected of launching the assault against Spamhaus.

Until these large attacks occurred, most DDoS incidences generated about 10 gbps of malicious traffic. Clearly, their severity is increasing. So is the frequency and length of attacks. Prolexic, a DDoS mitigation firm, found in its surveys that DDoS attacks increased 53% from 2011 to 2012. During this time, Prolexic mitigated seven attacks that exceeded 50 gbps. In this three-part series, we examine the anatomy of DDoS attacks. Part 1 describes how botnets are created and are used to launch attacks. Part 2 describes the types of DDoS attacks that can be used to disable your customer-facing systems. In Part 3, we discuss various mitigation strategies available for minimizing the effectiveness of a DDoS attack.


A single PC is not powerful enough to generate sufficient traffic to overwhelm most systems. It takes a concerted effort of many PCs to do so. This is a botnet. A botnet is a collection of infected systems that can be commanded to take a joint action upon request by a bot master. For DDoS attacks, this joint action is the generation of massive amounts of malicious data directed toward a victim’s web site.

There are several classes of botnets:

  • The earliest botnets were made up of infected PCs. Typically, a PC is infected by a Trojan that enters the PC via a malicious email, a malicious web site, or an infected web site. The Trojan opens a backdoor to the PC that allows the bot master to download its DDoS software into the PC. The PC then connects to the bot master and thereafter will be under its control. PCs cannot generate a great deal of traffic, primarily due to the bandwidths of their Internet connections. A megabit per second (mbps) is typical. Therefore, to generate ten gigabytes per second of traffic, the botnet must comprise ten thousand PCs.ddoschart2
  • Some attacks are politically popular and generate a great deal of support among a class of people around the world. In this case, attackers have enlisted many individuals to voluntarily contribute the services of their PCs to the botnet. The Islamic hackers that attacked U.S. banks in retaliation for the anti-Islamic YouTube video reportedly had access to hundreds of thousands of voluntarily provided PCs. Another example was an attack launched by supporters of Julian Assange, founder of WikiLeaks, when he was arrested for leaking classified material.
  • The limited capability of a PC to generate DDoS traffic is solved to a great extent by using powerful servers instead. In this case, servers are infected with DDoS software, often through known security vulnerabilities in popular programs such as Joomla and WordPress. A powerful server with wideband access to the Internet can generate a thousand times as much traffic as a PC.

Botnets for Rent

Botnets are readily available for rent on the darknet, private networks where connections are made only between trusted peers. Hackers form a community of trusted peers and can gain access to botnet rentals. The cost for botnets is relatively modest given the damage they can inflict. For instance, the following botnet rentals are advertised on the darknet:

  • 10,000 PCs – 10 gbps – $500 per month
  • 100,000 PCs – 100 gbps – $200 per day

Source: http://www.techproessentials.com/ddos-attacks-can-take-down-your-online-services/

Old and cheap modems are now being blamed for Spark’s broadband troubles.

Customers reported slow speeds and dropped connections over the weekend.

Spark now believes cyber criminals have gained access to a number of customer’s modems, and disrupted the network that way.

It has disconnected the affected modems, and contacting customers to discuss solutions.

Meanwhile, denial of service attacks which hobbled Spark’s internet over the weekend are extremely unlikely, according to an industry body.

Internet New Zealand’s work programme director Andrew Cushen says people arriving at work for the first time since Friday should run a virus scan on their computers.

But he doesn’t believe Spark will be a long-term target.

“These attacks are unfortunately quite common on the internet and they are used quite commonly overseas.

“We don’t see them often here in New Zealand, because denial of service attacks usually go after higher profile targets.”

Source: http://www.newstalkzb.co.nz/auckland/news/nbnat/2051865836-further-denial-of-service-attacks-on-spark-unlikely