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IEC (.iec)

.iec file signature | application/octet-stream

IEC is a legacy executable file format introduced by Microsoft for MS-DOS and later extended by Microsoft for Windows-based systems. It is used to start programs, deliver system utilities, and support older application and installer workflows on compatible operating systems. As a historical predecessor to newer Windows executable formats, it should be treated as untrusted code and opened only with appropriate security controls.

Safe

Magic Bytes

Offset 0
4D 5A

Sources: Wikipedia

Extension

.iec

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .iec files in Python

Python 
def is_iec(file_path: str) -> bool:
    """Check if file is a valid IEC by magic bytes."""
    signature = bytes([0x4D, 0x5A])
    with open(file_path, "rb") as f:
        return f.read(2) == signature

How to validate .iec files in Node.js

Node.js 
function isIEC(buffer: Buffer): boolean {
  const signature = Buffer.from([0x4D, 0x5A]);
  return buffer.subarray(0, 2).equals(signature);
}

How to validate .iec files in Go

Go 
func IsIEC(data []byte) bool {
    signature := []byte{0x4D, 0x5A}
    if len(data) < 2 {
        return false
    }
    return bytes.Equal(data[:2], signature)
}

API Endpoint

GET /api/v1/iec
curl https://filesignature.org/api/v1/iec

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .iec file?

A .iec file is identified by the magic bytes 4D 5A at byte offset 0. IEC is a legacy executable file format introduced by Microsoft for MS-DOS and later extended by Microsoft for Windows-based systems. It is used to start programs, deliver system utilities, and support older application and installer workflows on compatible operating systems. As a historical predecessor to newer Windows executable formats, it should be treated as untrusted code and opened only with appropriate security controls.

What are the magic bytes for .iec files?

The magic bytes for IEC files are 4D 5A at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .iec file?

To validate a .iec file, read the first bytes of the file and compare them against the known magic bytes (4D 5A) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .iec files?

There is no officially registered MIME type for .iec files. Systems typically use application/octet-stream as a generic fallback when handling this format.

Is it safe to open .iec files?

IEC (.iec) files are generally safe to open. They are classified as low risk because they primarily contain data rather than executable code. However, always ensure files come from a trusted source.