Overview Discussion

Overview Discussion

 Since “Cloud Computing” is a service . Read attached article and give a review on cloud computing using information given within article.

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Inside Risks Risks and Myths of Cloud Computing and Cloud Storage Considering existing and new types of risks inherent in cloud services.

insider misuse may create additional risks. All these risks are relevant to many different types of applications. As one example, from users’ perspectives, hav- ing unencrypted email maintained by a cloud provider may be particularly risky.

The basic concept of cloud comput- ing and cloud storage has a lineage spanning two generations, with sig- nificant experience in designing and administering these systems. Time-

C LOUD COMPUTING AND stor- age are often seen as gen- eral blessings, if not finan- cial salvations. There are good reasons behind this

claim. Cloud services are indeed usu- ally much cheaper than their dedi- cated counterparts. Administration and management oversight are sim- pler under a single, central authority. Small businesses and startups have taken advantage, using low-cost cloud services during their first few years. Cloud platforms are critical avenues to getting started for many companies, giving them access to many customers at low cost. Many business leaders see the cloud as an engine for small busi- nesses and job creation.

Cloud storage services are also a boon for individual users, most of whom do not back up their comput- ers and mobile devices regularly or at all. Cheap, automatic backup to cloud storage protects their valuable data from loss.

Despite all these bounties, cloud ser- vices also present new kinds of risks, which are considered here. Prospective cloud users should evaluate these risks before making their decisions about how to use clouds. The main issue is that expectations of trustworthiness may be unrealistic. Confidentiality, system in- tegrity, data integrity, reliability, robust- ness, resilience may be questionable. Protection against surveillance, and

denials of service are essential, as are perpetual access and long-term com- patibility of stored data. The integrity, accountability, and trustworthiness of potentially untrustworthy third parties and even unknown nth parties must also be considered. Those parties may have business models that are radically incompatible with user needs; further- more, they might go out of business— with users holding the bag. Moreover,

DOI:10.1145/2661049 Peter G. Neumann





compromises can be found in the ACM Risks Forum: http://www.risks.org.)

˲ Dropbox’s sharing services were hacked, resulting from a security hole in its link-sharing scheme. The ex- ploits were also disseminated by the perpetrators.

˲ No-IP had 22 of its most frequently used domains taken down by Micro- soft, under a seemingly overreaching federal court order.

˲ Amazon Web services have gone down (briefly) several times. Code Spaces (a valued source-code reposi- tory built using Amazon’s AWS facili- ties) was effectively destroyed by an at- tacker demanding ransom.

˲ Cisco Systems had a private crypto key embedded in their VoIP manager that allowed unauthorized control of sensitive messaging gear.

˲ Cryptolocker and other ransom- ware programs have forcibly encrypted stored information, and demanded payment to decrypt it (although in some cases have never done so even after receiving the ransom!). Although most of these attacks have been on in- dividual users, the opportunity for at- tacks on remote storage repositories is clearly a risk. (Recently, an antidote website has reportedly been created.)

˲ TrueCrypt (full disk encryption) was discontinued as source-available software by its pseudonymous authors, “as it may contain unfixed security is- sues.” (Uncertainty remains as to the severity and impact of those possible issues, and how they found their way into the codebase.)

˲ Similar things happened to Lavabit, which provided privacy and security fea- tures in email services to over 400,000 customers, but was then withdrawn after prolonged legal harassment that attempted to coerce the installation of surveillance equipment.

˲ Megaupload.com was taken down by authorities, blocking both illicit and legitimate users.

˲ Nirvanix went belly-up financially, giving its users two weeks to exit.

˲ Various talks at Black Hat and DEF CON in August were rather disenchant- ing. In short, essentially every device seems to be compromisable, often with a fixed master password embed- ded in the system, but with many more subtle vulnerabilities as well. This is old news to Inside Risks readers, but

sharing systems with common com- puting resources and possibilities for collaborative data access have been around since the 1960s (CTSS, Mul- tics, Tymshare), with varying types of sharing. Since the 1980s, Project Athena at MIT has employed the Sun Network File System, and later the Andrew File System, to provide three services that would be identified with today’s cloud services: remote stor- age of application programs, remote storage of personal files, and remote backup of personal files. However, time-sharing and Athena’s three ser- vices have been under single opera- tional administration, thus minimiz- ing the number of entities that users must trust (while at the same time providing a single point of failure). We know from experience how to off- set some of the risks when cloud ser- vices are the responsibility of a single administration. With respect to both local and remote servers, some of the risks can be reduced. For example, private systems and intranetworks under local control or more likely the control your own employers (with re- spect to hardware, software, certificate authorities, and pooled system and network administration) are likely to have greater trustworthiness.

What is new—and the source of new risks—is the scale and distributivity of some of the clouds. They are large dis- tributed systems with few centralized controls. Clouds that provide access to vast amounts of information (such as Google and Amazon) are extremely valuable resources. However, other clouds that store your own data (along with everyone else’s) can present seri- ous problems relating to trusting po- tentially untrustworthy entities.

Giving the “cloud” name to the old concept of large, shared, distributed systems is misleading. It creates a new buzzword, and hides the problems of risks that designers and admins have otherwise grappled with for years. Some of the cloud providers have ig- nored many of the old risks and are evi- dently largely oblivious to newer risks as well. Clearly, cloud computing is sim- ply remote computing, which was one of the primary reasons for the creation of the ARPANET—to allow people in one coastal time zone to benefit from un- used resources in other time zones at

certain hours of the day. This has clear- ly been an even greater benefit in the Internet, with its worldwide coverage. Similarly, cloud storage is simply remote storage, which in early days became common as off-site backup for obvious reasons of fault tolerance, emergency preparedness, and other reasons.

One risk in identifying remote stor- age for offsite backup as “cloud stor- age” is that this term masks the exis- tence of in-house alternatives, such as the common practice of periodically re- cording file-system snapshots on small detachable media, and keeping them in a safe place. This can be particularly important after nasty penetration at- tacks that may have compromised a system with the insertion of malware, sniffers, and so on. Furthermore, re- mote archiving—especially if widely distributed among different reposito- ries—leaves users unsure of whether their information is still retrievable in its original form (unless they have actu- ally retrieved it).

Ron Rivest has been quoted as say- ing, “Cloud computing sounds so sweet and wonderful and safe … we should just be aware of the terminology; if we [are] calling it swamp computing. I think you might have the right mind-set.”2

To paraphrase a quote often attrib- uted to Roger Needham, Butler Lamp- son, or Jim Morris, if you think cloud computing and cloud storage are the answer to your problems, you do not un- derstand those would-be solutions, and you do not understand your problems.

A few examples of relevant recent risky exploits are worth noting here. (Further background on the first nine items and other examples of cloud

Some of the cloud providers have ignored many of the old risks and are evidently largely oblivious to newer risks as well.





and also provide a means for sharing the information through out-of-band shared cryptographic keys. However, they remain vulnerable to other com- promises such as accidental or mali- cious deletion, lapse of contracts with remote providers, loss of cryptographic keys, unavailability of servers, invasive usage monitoring, and so on. As is true in general, key management becomes a fundamental risk in itself. Further- more, convenient schemes for recovery of lost keys (for example, backdoors) are always vulnerable to misuse—as are any backdoors that can be misused by insiders or external attacks.

Virgil Gligor1 has considered some of the risks inherent in virtualization in a context very similar to what is exam- ined in this column. Virtualization has certain aspects that are common to the abstractions provided by remote execu- tion and remote access, in the sense that there are well-defined interfaces for dealing with both cases—whether they are virtually remote or physically remote. There are also questions of the trustworthiness of the underlying mechanisms for enforcing the virtu- alization abstractions—for example, encapsulating, avoiding, or otherwise masking lower-layer vulnerabilities. Gligor’s article implicitly addresses some of the topics noted here, and de- serves a careful reading for those read- ers who would like further background than that included here.

I emphasize that clouds can of- fer real and significant benefits. They also bring many risks, which can be masked by the simplicity of the cloud abstraction. You should weigh these risks when designing, selecting, and configuring your cloud services.

References 1. Gligor, V. Security limitations of virtualization and how

to overcome them. Security Protocols Workshop, SPW 2010, Cambridge, U.K., 2010.

2. McMillan, R. Cloud computing a security nightmare, says Cisco CEO. Computerworld; http://www. computerworld.com/s/article/9131998/Cloud_ computing_a_security_nightmare_says_Cisco_CEO.

Peter G. Neumann (neumann@csl.sri.com) is Senior Principal Scientist in the Computer Science Lab at SRI International, and moderator of the ACM Risks Forum.

The author is enormously grateful to the members of the ACM Committee on Computers and Public Policy for their continued wisdom and counsel in acting as an advisory group for risks-related activities. This column gained significantly from their feedback.

Copyright held by author.

could be shocking to everyone else. Among old risks that are still per-

vasive, even in-house use of local stor- age can result in hardware outages and database software failures. Redundant copies might actually all wind up in a single vulnerable cloud repository. Furthermore, older data formats may no longer be supported. Local storage still requires attention to backup that can be successfully retrieved—in some cases many years later. Furthermore, if the original information is encrypted, the ability to manage and recover old keys becomes critical.

Recently, increasingly efficient cryp- tographic schemes are emerging in re- search communities for proof of data possession and proof of data retriev- ability. Unfortunately, simple and in- expensive techniques along these lines have not yet found their way from theory to practice. Perhaps more useful are the efforts cloud providers make to ensure their own data storage is recoverable. It may well be that, on average, cloud providers’ systems are better adminis- tered than the information technology groups of many organizations and agen- cies. At least, cloud users certainly hope so! Nevertheless, various risks remain.

Another old problem that has been exacerbated involves the ability to de- lete information ubiquitously. The existence of pervasive copies and dif- ferent versions has clearly exploded as a result of copies that have been repli- cated for resilience. Internet mirrors have proliferated far beyond anyone’s ability to keep track of unsearchable versions. With storage in some unac- countable remote repository, pervasive deletion will always seem to be ques- tionable. Besides, approaches that may succeed in pervasive deletion may also be victimized by accidental or mali- cious deletion. In this case, some sort of time machine would be desirable.

Many socially relevant risks also need to be considered, such as differ- ent versions of unauthentic data; the presence of misinformation in not quite identical searchable versions of what purports to be the same informa- tion; and situations in which people or organizations desire that certain infor- mation disappear completely.

Of course, international laws and regulations also present numerous problems—first by their imprecision

or overextension, and second by the uncertainty surrounding the origins and destinations of data and other resource requests. For example, if a nation insists that all information be- longing to its citizens must be stored within systems under its own legal jurisdiction, how can that be assured when it is so easy to subvert, and when ownership is itself murky? In addition, we must be cognizant of the risks of ubiquitous surveillance in unaccount- able and in some cases unknown re- mote resources.

As noted in many past Inside Risks columns (this is the 234th in the series), almost every computer or human en- tity is potentially untrustworthy, with respect to accidents, intentional mis- use, and attacks. As an example that remains problematic, the outsourcing of elections with regard to dependence on proprietary systems and software, computing resources, registration da- tabases, networks (whether open or pri- vate), and—above all—dependence on potentially untrustworthy people, aptly illustrates the end-to-end nature of the risks from the very beginning of the election cycle to the disputes that result from sources of error, fraud, and confu- sion—with concomitant fear, uncertain- ty, and doubt. Insider misuse is serious in all shared resources, but particularly in elections (numerous cases have been noted in the Risks Forum and else- where). In this example, outsourcing to unaccountable entities is problematic.

Despite the risks discussed here, there are some hopes for constructive alternatives. Research communities have various approaches to pieces of this puzzle, but rarely to systems as a whole. As a result, many of the previ- ous columns in this series are relevant to the use or misuse of remote resourc- es—even if they focused on problems that were previously considered as lo- cal. For example, cryptography that is managed solely by end users for infor- mation stored remotely in encrypted forms is often touted as a solution to the problem of having to trust an un- trustworthy remote storage provider. Homomorphic cryptography has the potential to allow computations on en- crypted information, without the need for that information to be decrypted. These approaches can improve the confidentiality of the information,