Jitter

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Jitter

What it is

Jitter is an anti-skimming technique used in card readers and ATMs that deliberately alters the motion or speed of a card as it is pulled into the machine. By introducing a stop-start or stutter in the card draw, jitter aims to disrupt the steady magnetic-stripe readout that illegal skimming devices require, making any copied data unreadable or corrupted.

How it works

  • Jitter is implemented in motorized card readers that draw the card into the machine for scanning.
  • Instead of a smooth, continuous read, the reader intermittently pauses or varies the card speed during the magnetic-stripe scan.
  • Many skimmers depend on a consistent swipe or feed to capture stripe data; jitter’s irregular timing reduces the success rate of those devices.
  • Jitter is generally not effective on dip readers or machines where users insert and manually remove their card (manual “dip” or swiped readers).

Limitations

  • Jitter is not foolproof. Skilled criminals and advanced skimming devices have found ways to circumvent it.
  • It can interfere with legitimate reads, causing legitimate transactions to fail or require repeated attempts.
  • The technique only applies to motorized readers; ATMs and terminals with manual dip or swipe mechanisms are not protected by jitter.
  • As skimming technology has evolved, jitter’s overall effectiveness has declined, and it should not be relied on as the sole anti-skimming defense.

Practical tips for consumers

  • Prefer chip or contactless (NFC) transactions when available; these are more secure than magnetic-stripe reads.
  • Use ATMs located inside bank branches or well-lit, busy locations when possible.
  • Inspect the card slot and surrounding area for loose, bulky, or unusual attachments before inserting your card.
  • Cover the PIN pad when entering your PIN and be wary of devices or cameras aimed at the keypad.
  • Monitor account activity regularly and report suspicious charges or devices to your bank immediately.

Key takeaways

  • Jitter introduces irregular motion during card reads to frustrate magnetic-stripe skimmers.
  • It is useful primarily in motorized, draw-in card readers (common in some ATMs) and is ineffective on manual dip readers.
  • Jitter reduces skimming success but is not a complete solution—consumers and institutions should use additional security measures.