Cloud services continue to enjoy great popularity. Most vendors compete to see who can provide more capacity for a lower price, but other considerations are also important. For instance, many users wonder which service will be better at protecting privacy.

Cloud services are often used for collaborative work when it is essential to keep the data of all participants in sync. Many services also offer a version history that can be used to understand changes to files. However, because of the growing storage quotas, many users also use the services for file sharing – not least because many email providers continue to limit the maximum size of file attachments to a few megabytes. In such cases, cloud storage provides a convenient option for distributing data by setting up appropriate shares.

In this article, I consider security and privacy, as well as the free storage quota and ergonomics for manually uploading and downloading files.

Copy

The provider Copy [1] belongs to the California company Barracuda Networks Inc., which enjoys a good reputation internationally as a developer of security solutions in the IT sector. However, the servers are located in the United States, making them less suitable for storing sensitive data. A look at the privacy policy [2] will confirm this: Copy reserves several options for the use of its customers' private data.

The company offers 15GB of free storage space for each user that registers on the website. This can be increased to 20GB through loyalty programs, such as inviting new users. If you need more space, you can receive 250GB of storage space as a private client with the "Pro" version at a price of $4.99 per month. Copy offers special "Company" tariffs for one or more terabytes of storage capacity. The pricing here is also determined by the number of users.

Copy provides both the mandatory web interface and special client software for multiple platforms for managing and using the service. Linux users download a TGZ archive of almost 50MB from the website via the Install desktop app link and install the program. The graphic client, called up in the terminal with the ./CopyAgent command, initially either allows you to log on to an existing account or create a new one. The program creates a folder called Copy, whose contents it subsequently aligns with cloud storage on the local hard disk.

An active Copy agent places an icon in the system tray of the desktop. Right-clicking it opens a context menu. Here you can access the cloud service's most important basic functions. You can configure settings in the Preferences window, which you can access via the main menu (Figure  1).

Figure 1: The Copy file host offers very intuitive client software.

To make files accessible to other users, click on the Visit Copy website entry in the system tray in the applet menu. Your personal page for the service will then appear in the browser; it lists the files contained in the cloud on the right-hand side. Select the files to be shared here by right-clicking and selecting the Share menu item from the context menu. Then, specify the recipient by entering an email address (Figure 2). The service allows you to share the object with multiple users or groups and to establish special rights regarding the share.

Figure 2: The Copy service offers several options for sharing your files with others.

The recipient can view the received file, including the given rights in the in the Received tab, via Preferences | Sharing (Figure 3). Double-clicking the file name will open the Copy website and allow access. Subject to the rights assigned, other file operations may also be possible.

Figure 3: Copy displays this screen to the recipient of a shared file.

Dropbox

Dropbox is one of the world's largest cloud providers and is considered a pioneer in this area. The service is also suitable for use in heterogeneous IT environments thanks to the client applications for multiple platforms. Dropbox uses Amazon's  S3 web service for storage. The service transmits the packets in encrypted form and also stores them AES-encrypted in the cloud. However, as Dropbox itself stores the private key, there is no secure end-to-end encryption. The provider also reserves full access rights to your stored data for the cases in which it is obliged to do so [3].

The company offers the setup for Linux in DEB and RPM format and as a source for download [4]. This is an initialization program, which only downloads and installs the actual Dropbox client after starting; it then opens and retrieves the access data. If you have not registered yet, you can do so by clicking on Register in the login window. Dropbox also creates a folder of the same name on the local hard disk when you log in for the first time; the software saves the data to be synchronized in this folder.

The free storage quota (only 2GB) is significantly lower than that of Copy. However, Dropbox also offers options for increasing the available storage space by recruiting new members, for example. The company merely provides one option for private users in the form of a 1TB upgrade, which costs $9.99 per month or $99 per year. The price for use in companies depends on storage size and number of users.

Sharing files in Dropbox is similar to Copy and occurs via the website by first creating a folder in which you save the contents to be shared. You can do this either in the local Dropbox folder using the file manager or by dragging and dropping in the web browser. After successfully uploading files to the cloud, click on the folders to be shared in the web GUI; the Share button will then appear to the right on the line. Clicking on it opens an options window where you choose whether you just want to send a download link or whether the recipient should be allowed to edit the shared data directly (Figure  4).

Figure 4: In Dropbox, you can easily share your data with other users via the web GUI or send them share links via email.

After selecting a sharing option, the next window prompts you to invite users. As with Copy, you enter the email address of recipients who should receive access to the shares here. After receiving the message, the recipients then decide whether to accept or decline the invitation. If the recipients already have a Dropbox account, the service integrates the shared data into their storage after acceptance. They can also see in the web browser which users are allowed to access the shared data (Figure  5).

Figure 5: The recipient of shared Dropbox files receives detailed information about the share.

Google Drive

The search engine giant Google, like Copy and Dropbox, comes from the United States and is therefore also subject to the US Patriot Act. The Google Drive cloud service provides you with 15GB of free storage, which you can expand as required through various subscription models for a cost. The prerequisite for using Google Drive is a single sign-on, which is true for all other Google services. Note that Google still does not offer a Linux client. Resourceful developers utilize this deficit and offer a commercial Linux client called Insync [5].

Unlike most free cloud services, Google requires that you provide a multitude of personal information, such as date of birth, phone number, or email address when logging on. The service checks that the data is plausible as it is being entered.

Google sends you an opt-in email to the specified email address before activating your account; if you specify a phone number, you will also receive a text message. You verify the number as yours by entering the confirmation code on the registration page. After successfully registering, you will receive direct access to all services. Google Drive welcomes you with a tidy web interface.

To begin, you create and name a new folder in the Google Drive web interface by clicking on the red New button on the left side of the window. To copy files into it, select New. If you want to share content with other users, you need to send a share link for the object. You can get this by clicking the object in question in the overview with the right mouse button and selecting Share from the context menu. In the subsequent dialog, you enter the recipients' email addresses and define their rights to the file (Figure  6).

Figure 6: Google Drive reduces the sharing settings to the essentials.

Google also allows shares to recipients who do not have a Google account. The services makes this known after the file or folder has been released by sending an invitation email from which the linked content can be accessed. However, Google does not yet send back any revisions to the original sender.

Members of Google Drive receive an overview of the shared contents in the Shared with me pane in the web browser and can continue to edit shared files subject to the rights granted. The Office packet provided by Google online also lets you collaborate on documents without using a locally installed Office suite.