This is counter to the quick, intuitive interfaces which are supposed to be a hallmark of Web 2. Additionally, this packer has to include a significant amount of unpacking logic. That logic is implemented in code attached to every packed script, which means there are many common blocks of script for which the packed script is actually larger than the original.
A small less than 50 KB packed JavaScript file is smaller than typical packed benign libraries and the size itself is a sign of possily malicious code. The unpacking stub itself uses some dubious functions. From the JSLint documentation section titled "eval is evil":. This is sometimes necessary, but in most cases it indicates the presence of extremely bad coding.
The eval function is the most misused feature of JavaScript. The eval function lies at the heart of the Dean Edwards packer. It is seen so often in obfuscated malicious JavaScript that many security companies protect clients from new JavaScript threats via heuristics based on statistical analysis of the use of eval in combination with other functions, the combination of which is seen almost exclusively in code designed to bypass other filters ad blockers or anti-virus, for example. The Dean Edwards packer makes it difficult to tell benign code from malicious code.
Although it does not operate on a parser stream, its design allows it to safely pack pre-obfuscated exploits which may include patterns ambiguous to other pattern-based packers.
This makes it attractive to attackers. Because of its use of eval combined with other certain methods such as String. This would normally mean that attackers would gain nothing towards evasion by using it. However, it is now being used more in known malicious scripts than in known benign code. Because the Dean Edwards packer output is so similar to malicious code, but so widely used in benign code -- consider the popularity of IE7.
Researchers have verified the whitelist status of this packer in at least one product by placing this stub around known exploit code. The exploit code alone generated an alert, which the unpacked exploit code surrounded by the packer stub sailed right through.
For years, in detecting malicious code using this packer, the risk of a false negative was very small compared to a risk of a false positive. It simply wasn't used by the cyber underground. That all changed with the success of an XSS worm which infected , users of the Orkut social networking service in November In December , a couple of security companies' products began blocking packed scripts with new signature updates.
Because of complaints of false alarms from end users, both relented, leaving their customers at risk of encountering new packed exploits. In fact, shortly after re-whitelisting packed scripts, a SQL injection flaw in the web site of one of the security companies, allowed attackers to place script directing visitors to, ironically or not? Would-be attackers took notice, documented the whitelist status, and began packing their wares in order to successfully evade filters.
One actual attack used both packed and unpacked versions of another RealPlayer exploit so the attackers could study the relative effectiveness of the use of this packer to evade filters.
Heuristics often fail when encountering "Trojaned libraries" which are actually copies of common libraries laced with exploit code. These look and even function -- except under one unique circumstance or trigger -- identical to their benign counterparts.
The files could be named the same as well. Packing increases the chance that heuristics will fail to detect previously unknown exploits, such as the packed 0-day QuickTime exploit uncovered in January By default, this is about 40 GB.
When set to hda, the audio controller is Intel HD Audio. When set to sb16, the audio controller is SoundBlaster When set to none, the graphics controller is disabled. By default, this is 4 MiB.
When set to true, 3D acceleration is enabled. When set to false, 3D acceleration is disabled. By default, no screen resolution is set. By default this is other, but you can get dramatic performance improvements by setting this to the proper value. To view all available values for this run VBoxManage list ostypes. Setting the correct value hints to VirtualBox how to optimize the virtual hardware to work best with that operating system.
The size of the cleared area must be at least 1MB. When set to pcie, the drive is attached to an NVMe controller. When set to virtio, the drive is attached to a VirtIO controller. Please note that when you use "pcie", you'll need to have Virtualbox 6, install an extension pack and you will need to enable EFI mode for nvme to work, ex:. Increasing this value can be useful if you want to attach additional drives. VirtualBox supports up to ports on a maximum of 1 NVMe controller.
Each value represents the disk image size in MiB. Each additional disk uses the same disk parameters as the default disk. Unset by default. Defaults to false. When enabled, Packer will not export the VM.
Useful if the build output is not the resultant image, but created inside the VM. Valid options are upload , attach , or disable. If the mode is attach the guest additions ISO will be attached as a CD device to the virtual machine. The default value is upload. If disable is used, guest additions won't be downloaded, either.
Options are "ide" and "sata". By default this is VBoxGuestAdditions. This is a configuration template where the Version variable is replaced with the VirtualBox version. By default the checksums will be downloaded from the VirtualBox website, so this only needs to be set if you want to be explicit about the checksum.
By default, the VirtualBox builder will attempt to find the guest additions ISO on the local file system. If it is not available locally, the builder will download the proper guest additions ISO from the internet. The type of the checksum can also be omitted and Packer will try to infer it based on string length. Here is a list of valid checksum values:. Packer will try these in order. If anything goes wrong attempting to download or while downloading a single URL, it will move on to the next.
All URLs must point to the same file same checksum. By default will go in the packer cache, with a hash of the original filename and checksum as its name. This defaults to iso.
The files in this directory will be available over HTTP that will be requestable from the virtual machine. This is useful for hosting kickstart files and so on. By default this is an empty string, which means no HTTP server will be started. This is covered in more detail below. By default this is empty, which means no HTTP server will be started.
Because Packer often runs in parallel, Packer will choose a randomly available port in this range to run the HTTP server. If you want to force the HTTP server to be on one port, make this minimum and maximum port the same.
By default the values are and , respectively. Defaults to 0. A floppy can be made available for your build. This is most useful for unattended Windows installs, which look for an Autounattend. By default, no floppy will be attached. All files listed in this setting get placed into the root directory of the floppy and the floppy is attached as the first floppy device.
The summary size of the listed files must not exceed 1. Currently, no support exists for creating sub-directories on the floppy. Directory names are also allowed, which will add all the files found in the directory to the floppy.
This is useful for when your floppy disk includes drivers or if you just want to organize it's contents as a hierarchy. The keys represent the paths, and the values contents. An iso CD containing custom files can be made available for your build. By default, no extra CD will be attached.
All files listed in this setting get placed into the root directory of the CD and the CD is attached as the second CD device. Defaults to zero 0. Zero means an error will not be retried. The file provisioner is also able to upload a complete directory to the remote machine. When uploading a directory, there are a few important things you should know. First, the destination directory must already exist.
If you need to create it, use a shell provisioner just prior to the file provisioner in order to create the directory. If the destination directory does not exist, the file provisioner may succeed, but it will have undefined results. Next, the existence of a trailing slash on the source path will determine whether the directory name will be embedded within the destination, or whether the destination will be created.
An example explains this best:. The foo directory on the remote machine will be created by Packer. This behavior was adopted from the standard behavior of rsync. Note that under the covers, rsync may or may not be used. In general, local files used as the source must exist before Packer is run. This is great for catching typos and ensuring that once a build is started, that it will succeed. However, this also means that you can't generate a file during your build and then upload it using the file provisioner later.
A convenient workaround is to upload a directory instead of a file. The directory still must exist, but its contents don't.
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