The cloud has been around for some time now and is still gaining popularity in every day operations of IT companies. I’ve seen different companies with operational models 90% based on cloud services, where the rest of the 10% is constituted of in-house servers. The basic response after asking about security issues related to cloud services was that the cloud service provider will take care of them and they don’t have to worry about it. This isn’t necessarily the case with every cloud service provider, since some CSPs have a good security model in place, while others clearly do not. There are many advantages of the cloud services, which are why the cloud service model is being used extensively, but they are out of scope of this article.
Before continuing with the article, let’s quickly describe the difference between a threat and a vulnerability we’ll be using throughout the article [4, 5]:
Vulnerability: is a weakness that can be exploited by the attacker for his own personal gain. A weakness can be present in software, environments, systems, network, etc.
- Threat: is an actor who wants to attack assets in the cloud at a particular time with a particular goal in mind, usually to inflict his own financial gain and consequentially financial loss of a customer.
Cloud Computing Vulnerabilities
When deciding to migrate to the cloud, we have to consider the following cloud vulnerabilities :
Session Riding: session riding happens when an attacker steals a user’s cookie to use the application in the name of the user. An attacker might also use CSRF attacks in order to trick the user into sending authenticated requests to arbitrary web sites to achieve various things.
Virtual Machine Escape: in virtualized environments, the physical servers run multiple virtual machines on top of hypervisors. An attacker can exploit a hypervisor remotely by using a vulnerability present in the hypervisor itself – such vulnerabilities are quite rare, but they do exist. Additionally, a virtual machine can escape from the virtualized sandbox environment and gain access to the hypervisor and consequentially all the virtual machines running on it.
Reliability and Availability of Service: we expect our cloud services and applications to always be available when we need them, which is one of the reasons for moving to the cloud. But this isn’t always the case, especially in a bad weather with a lot of lightning where power outages are common. The CSPs have uninterrupted power supplies, but even those can sometimes fail, so we can’t rely on cloud services to be up and running 100% of the time. We have to take a little downtime into consideration, but that’s the same when running our own private cloud.
- Insecure Cryptography: cryptography algorithms usually require random number generators, which use unpredictable sources of information to generate actual random numbers, which is required to obtain a large entropy pool. If the random number generators are providing only a small entropy pool, the numbers can be brute forced. In client computers, the primary source of randomization is user mouse movement and key presses, but servers are mostly running without user interaction, which consequentially means lower number of randomization sources. Therefore the virtual machines must rely on the sources they have available, which could result in easily guessable numbers that don’t provide much entropy in cryptographic algorithms.
- Data Protection and Portability: when choosing to switch the cloud service provider for a cheaper one, we have to address the problem of data movement and deletion. The old CSP has to delete all the data we stored in its data center to not leave the data lying around. Alternatively, the CSP that goes out of the business needs to provide the data to the customers, so they can move to an alternate CSP after which the data needs to be deleted. What if the CSP goes out of business without providing the data? In such cases, it’s better to use a widely used CSP which has been around for a while, but in any case data backup is still in order.
- CSP Lock-in: we have to choose a cloud provider that will allow us to easily move to another provider when needed. We don’t want to choose a CSP that will force us to use his own services, because sometimes we would like to use one CSP for one thing and the other CSP for something else.
- Internet Dependency: by using the cloud services, we’re dependent upon the Internet connection, so if the Internet temporarily fails due to a lightning strike or ISP maintenance, the clients won’t be able to connect to the cloud services. Therefore, the business will slowly lose money, because the users won’t be able to use the service that’s required for the business operation. Not to mention the services that need to be available 24/7, like applications in a hospital, where human lives are at stake.
Cloud Computing Threats
Before deciding to migrate to the cloud, we have to look at the cloud security vulnerabilities and threats to determine whether the cloud service is worth the risk due to the many advantages it provides. The following are the top security threats in a cloud environment [1, 2, 3]:
Ease of Use: the cloud services can easily be used by malicious attackers, since a registration process is very simple, because we only have to have a valid credit card. In some cases we can even pay for the cloud service by using PayPal, Western Union, Payza, Bitcoin, or Litecoin, in which cases we can stay totally anonymous. The cloud can be used maliciously for various purposes like spamming, malware distribution, botnet C&C servers, DDoS, password/hash cracking, etc.
- Secure Data Transmission: when transferring the data from clients to the cloud, the data needs to be transferred by using an encrypted secure communication channel like SSL/TLS. This prevents different attacks like MITM attacks, where the data could be stolen by an attacker intercepting our communication.
- Insecure APIs: various cloud services on the Internet are exposed by application programming interfaces. Since the APIs are accessible from anywhere on the Internet, malicious attackers can use them to compromise the confidentiality and integrity of the enterprise customers. An attacker gaining a token used by a customer to access the service through service API can use the same token to manipulate the customer’s data. Therefore it’s imperative that cloud services provide a secure API, rendering such attacks worthless.
- Malicious Insiders: employees working at cloud service provider could have complete access to the company resources. Therefore cloud service providers must have proper security measures in place to track employee actions like viewing a customer’s data. Since cloud service provides often don’t follow the best security guidelines and don’t implement a security policy, employees can gather confidential information from arbitrary customers without being detected.
- Shared Technology Issues: the cloud service SaaS/PasS/IaaS providers use scalable infrastructure to support multiple tenants which share the underlying infrastructure. Directly on the hardware layer, there are hypervisors running multiple virtual machines, themselves running multiple applications. On the highest layer, there are various attacks on the SaaS where an attacker is able to get access to the data of another application running in the same virtual machine. The same is true for the lowest layers, where hypervisors can be exploited from virtual machines to gain access to all VMs on the same server (example of such an attack is Red/Blue Pill). All layers of shared technology can be attacked to gain unauthorized access to data, like: CPU, RAM, hypervisors, applications, etc.
- Data Loss: the data stored in the cloud could be lost due to the hard drive failure. A CSP could accidentally delete the data, an attacker might modify the data, etc. Therefore, the best way to protect against data loss is by having a proper data backup, which solves the data loss problems. Data loss can have catastrophic consequences to the business, which may result in a business bankruptcy, which is why keeping the data backed-up is always the best option.
- Data Breach: when a virtual machine is able to access the data from another virtual machine on the same physical host, a data breach occurs – the problem is much more prevalent when the tenants of the two virtual machines are different customers. The side-channel attacks are valid attack vectors and need to be addressed in everyday situations. A side-channel attack occurs when a virtual machine can use a shared component like processor’s cache to access the data of another virtual machine running on the same physical host.
- Account/Service Hijacking: it’s often the case that only a password is required to access our account in the cloud and manipulate the data, which is why the usage of two-factor authentication is preferred. Nevertheless, an attacker gaining access to our account can manipulate and change the data and therefore make the data untrustworthy. An attacker having access to the cloud virtual machine hosting our business website can include a malicious code into the web page to attack users visiting our web page – this is known as the watering hole attack. An attacker can also disrupt the service by turning off the web server serving our website, rendering it inaccessible.
- Unknown Risk Profile: we have to take all security implications into account when moving to the cloud, including constant software security updates, monitoring networks with IDS/IPS systems, log monitoring, integrating SIEM into the network, etc. There might be multiple attacks that haven’t even been discovered yet, but they might prove to be highly threatening in the years to come.
- Denial of Service: an attacker can issue a denial of service attack against the cloud service to render it inaccessible, therefore disrupting the service. There are a number of ways an attacker can disrupt the service in a virtualized cloud environment: by using all its CPU, RAM, disk space or network bandwidth.
- Lack of Understanding: enterprises are adopting the cloud services in every day operations, but it’s often the case they don’t really understand what they are getting into. When moving to the cloud there are different aspects we need to address, like understanding how the CSP operates, how the application is working, how to debug the application when something goes wrong, whether the data backups are already in place in case the hard drive dies, etc. If the CSP doesn’t provide additional backup of the data, but the customer expects it, who will be responsible when the hard drive fails? The customer will blame the CSP, but in reality it’s the customer’s fault, since they didn’t familiarize themselves enough with the cloud service operations – the result of which will be lost data.
- User Awareness: the users of the cloud services should be educated regarding different attacks, because the weakest link is often the user itself. There are multiple social engineering attack vectors that an attacker might use to lure the victim into visiting a malicious web site, after which he can get access to the user’s computer. From there, he can observe user actions and view the same data the user is viewing, not to mention that he can steal user’s credentials to authenticate to the cloud service itself.
In this article we’ve taken a look at the top cloud vulnerabilities and threats that need to be addressed when moving to the cloud. When an enterprise company wants to move their current operation to the cloud, they should be aware of the cloud threats in order for the move to be successful. We shouldn’t rely on the cloud service provider to take care of security for us; rather than that, we should understand the security threats and communicate with our CSP to determine how they are addressing the security threats and continue from there. We should also create remote backups of our data regardless of whether the CSP is already providing backup service for us – it’s better to have multiple data backups than figure out the data was not backed up at all when the need for data restoration arises.
 Top Threats to Cloud Computing V1.0, Cloud Security Alliance, March 2010,
 CCSP Boot Camp
 The Notorious Nine Cloud Computing Top Threats in 2013, February 2013,
 Seven Deadly Threats and Vulnerabilities in Cloud Computing,
 Being Vulnerable to the Threat of Confusing Threats with Vulnerabilities,
 Difference Between Threat, Vulnerability and Risk,