In the Scan section, provide a name and description for your scan.

For Custom scans, this information appears on the tile of the related scan (visible from Protection ▸ Antivirus ▸ Other scans) so that you can easily recognize it.

In Scan areas, use the drop-down menu to select the data space you want the scan to analyze. You can choose to scan any of the following areas:

• Storage drives and removable media: the options in this section apply to data that is stored on physical devices such as hard disks and USB sticks.
• Auto-start programs and modules loaded in memory: the options in this section apply to applications and processes that launch after system startup or run in the background.
• Interactive selection: this option prompts you to specify a location on your PC each time you run the scan.
• Rootkits: select from levels of thoroughness with Rootkits full scan being the most thorough, but slowest option.

To add another area to the list, click Add. To remove an area, click the relevant row, then click Delete.

In File types, configure your scan to analyze all files within the defined area by selecting Scan all files (slowest). Alternatively, configure your scan to only analyze files that are typically vulnerable to malware by selecting one of the following options:

• Content (slow): the scan determines the format of each file according to its content, then scans the files identified as typically vulnerable to malware. This option is useful if file content differs from the extension type in the file name.
• Name extension (fast): the scan analyzes only files with risky extension types in the file name, such as .exe, .com, .bat. Alternatively you can specify the extension types you want the scan to analyze by clicking Add. In this case, only the specified extension types are scanned.

Note: For new custom scans, Content is selected by default as it provides the optimal balance between thoroughness and speed. Scan all files is the most thorough option, but also the slowest.

The Sensitivity screen allows you to define the following settings for the scan:

• Heuristics: heuristics enable Avast to detect unknown malware by analyzing code for commands which may indicate malicious intent. Specify your preferences for the following options:
  • Use the orange bars to indicate your preferred level of heuristic sensitivity. The default setting for new custom scans is Normal (three bars). With higher sensitivity, Avast is more likely to detect malware, but also more likely to make false-positive detections (incorrectly identify files as malware).
  • Tick Use Code Emulation to unpack and test any suspected malware in an emulated environment where the file cannot cause damage to your PC. This option is ticked by default for new custom scans.
• Sensitivity: tick Test whole files if you want the scan to analyze entire files rather than only the parts typically affected by malicious code. When this option is ticked, the scan is slower but more thorough.
• PUP and suspicious files: tick Scan for potentially unwanted programs (PUPs) if you want the scan to look for programs that are stealthily downloaded with other programs and typically perform unwanted activity.
• Links: tick Follow links during scan to allow Avast to scan other files used by the files being scanned for potentially harmful content. This option is ticked by default for new custom scans.

Note: The more options you tick and the higher the sensitivity you set, the more thoroughly Avast checks your PC. With higher sensitivity, scans run slower, false-positive detections are more likely, and more resources are consumed on your PC.

The Packers screen allows you to indicate the compressed file types that you want Avast to unpack during the scan, for example, .zip, and .rar. Scans are better able to analyze files for malware when files are unpacked. To unpack a file is the same as to extract a file from an archive. Original archives, including the files contained within, remain intact during scans.

By default, Self-extracting archives, Droppers and NTFS streams are ticked for new custom scans. Other archive types do not need to be scanned because unless they are extracted, they cannot harm your PC. If you tick All packers, the scan analyzes all archive files, which significantly increases the scan duration.

Note: For more information about a specific file type, tick the file type and refer to the information under Packer description at the bottom of the screen.

The Actions screen allows you to configure automatic responses to any threats detected by the scan.

Follow these steps:

1. Tick Automatically apply actions during scan (unticked by default for new custom scans).
2. Select a file type (Virus, PUP or Suspicious), then select the action you want the scan to apply:
   Note: You can specify different actions for each detection type.
   • Fix automatically: attempts to repair the file. If unsuccessful, moves the file to the Virus Chest or deletes the file if neither action is successful.
   • Move to Chest: sends the file to the Virus Chest where the file cannot harm your system.
   • Repair: removes malicious code if the file is only partially infected. This action is not possible if the entire code is malware.
   • Delete: permanently removes the file from your PC.
   • No action: makes no changes to the contents or location of the file (not recommended as an automatic action).
3. Tick If necessary, perform the selected action at the next restart to apply actions when you next restart your PC, if the action requires it (ticked by default for new custom scans).
4. Specify the action you want to take if the scan detects a malicious or suspicious file or program contained in an archive (specified in Packers):
   • Try to remove only the packed file from the archive; if it fails, do nothing (default option for new custom scans): attempts to remove the contained file or program but does not delete the entire archive.
   • Try to remove only the packed file from the archive; if it fails, remove the whole containing archive: deletes the entire archive if unable to remove the file or program contained within.
   • Always remove the whole archive: deletes the entire archive.
5. Click OK.

Define the following settings for the scan:

• Scan priority: use the orange bars to indicate the scan's level of importance when other applications are running on your system. Higher priority enables the scan to run faster, but slows down other applications. Normal (two bars) is the default setting for new custom scans.
• Speed up scanning by using the persistent cache: enables the scan to refer to information retained from previously scanned files. Trusted files which have already been verified as safe are not scanned again which enables scans to process faster. This option is ticked by default for new custom scans.
• Store data about scanned files in the persistent cache: stores data about scanned files in your system's permanent memory so that future scans can refer to this data and run faster. The information stored in persistent cache is not lost after a system restart or virus definitions update.
• Speed up scanning by reading files in the order they are stored on disk: reduces the amount of time the scan takes to locate stored data by scanning files in the order that their physical data is stored on the disk (faster) rather than the order that the files are organized in the file system (slower). This option is ticked by default to make new custom scans run faster, however, it is only effective for NTFS (New Technology File System) formatted drives.

The Report file screen allows you to specify whether you want the scan to produce a report at the end of each scan. When troubleshooting issues with Avast Support representatives, you may be requested to provide a report file.

To generate automatic scan reports, follow these steps:

1. Tick Generate report file.
2. Manage the following settings:
   • File name: provide a name for the report file.
   • File type: select the format of the report file - plain text ANSI, plain text Unicode, or XML.
   • If file exists: select Append if you want new results to be added to the end of the previous report, or Overwrite if you want new results to replace the previous report.
3. Define the contents of the report:
   • Infected items: files and areas of the scanned environment which are identified as containing malware. This option is ticked by default.
   • Hard errors: unexpected errors which require further investigation. This option is ticked by default.
   • Soft errors: minor errors such as a file being unable to be scanned because it was in use.
   • OK items: files and areas which were identified as being clean. Ticking this option results in very long reports.
   • Skipped items: files and areas which the scan did not check because of the scan settings.
4. Click OK.

Report files are saved in one of the following locations:

• Windows 10, Windows 8.1, Windows 8, Windows 7, or Windows Vista: C:\ProgramData\Avast Software\Avast\report
• Windows XP: C:\Documents and Settings\All Users\Application Data\Avast Software\Avast\report

The Exclusions screen allows you to specify files or folders that you want the scan to ignore. To add a new item, type its location manually into the text box or click Browse, tick the relevant folder, then click OK.

To add another location to the list, click Add. To remove a location, click the relevant row, then click Delete.

File and folder locations can include wildcard characters ? and *. The asterisk replaces zero or more characters, and the question mark replaces a single character. For example:

• To exclude all HTML files, type *.htm* into the text box.
• To exclude a folder and its sub-folders, add \* to the end of the folder name, for instance C:\example\* .
• To exclude all files labeled in a certain way on any of your hard drives, include ?:\ in front of the path, for instance ?:\example.exe .

Note: Exclusions that you specify on this screen only apply to the selected scan and do not affect any other scans or Shields. If you want to exclude a location from all Avast Antivirus scans, go to Settings ▸ General ▸ Exclusions to specify the location.

To schedule the scan, follow these steps:

1. Tick Schedule this scan and specify if you want the scan to run on just one occasion (Once) or periodically (Daily, Weekly, or Monthly).
2. Manage your preferences for the following options:
   • Do not start the scan if running on batteries: tick to ignore schedule settings if your PC is not connected to a power source.
   • Pause the scan if batteries mode begins: tick to pause the scan if your PC is removed from its power source during the scan.
   • Wake up the system to start the scan (if in sleep mode): tick to run the scheduled scan even if your PC is in power-saving mode.
   • Shut down the system after the scan finishes: tick to automatically turn off your PC after the scan.
3. Set the time that you want the scan to run in 24-hour format (for example, instead of 3pm use 15:00).
4. Specify the day that you want the scan to run.
5. Click OK.

Note: Scheduled scans are unable to run when your PC is switched off.