Top Ten Most Disastrous Software Bugs

Top 10 Disastrous Programming Bugs in History

10. AT&T Network Failure (1990)

  • Date: January 15, 1990

  • Incident: Upgrade of complex software led to network crash

  • Impact:

    • 75 million missed phone calls

    • 200,000 airline reservations canceled

    • Estimated loss of $60 million

  • Cause: Rapid message delivery caused switching centers to reset continuously.

  • Outcome: Despite losses, AT&T recovered.

9. Mariner One Launch Failure (1962)

  • Date: 1962

  • Incident: Launch of the unmanned Mariner One spacecraft ended in failure

  • Impact: Lost $135 million

  • Cause: Self-destruct command issued due to miscalculation caused by a missing overbar in a mathematical equation.

  • Outcome: Successful launch of Mariner 2 five weeks later.

8. Mars Climate Orbiter Loss (1999)

  • Date: September 23, 1999

  • Incident: Mars Climate Orbiter lost contact during orbit insertion

  • Impact: Cost $327 million

  • Cause: A line of code mixed US customary units with metric units for calculations.

  • Outcome: Improved processes based on lessons learned; water discovered on Mars later.

7. Knight Capital Stock Market Glitch (2012)

  • Date: August 1, 2012

  • Incident: Release of untested software caused massive stock fluctuations

  • Impact:

    • Knight’s stock plummeted 33% initially

    • Total loss of $440 million

  • Cause: Obsolete function triggered by missing code on a server leading to erratic stock pricing.

  • Outcome: Knight Capital acquired by GetGo LLC in 2013.

6. Intel Pentium Bug (1994)

  • Date: 1994

  • Incident: Floating point calculation failure in original Pentium processors

  • Impact: Cost Intel $475 million for replacements

  • Cause: Bug affected calculations beyond the third decimal point, problematic for mathematics and science applications.

  • Outcome: Intel remains a leading provider of PC parts.

5. THEIC 25 Radiation Therapy Machine Flaw (1985)

  • Date: 1985

  • Incident: Software bug in THEIC 25 led to incorrect dosage in radiation therapy

  • Impact: Resulted in six patient deaths

  • Cause: Bug caused machine to deliver megavolt doses instead of low-dose treatments.

4. Cobalt 60 Overdose Incident (2000)

  • Date: 2000

  • Incident: Cobalt 60 machine in Panama led to overdose in radiation therapy

  • Impact: 24 patient deaths due to miscalculation of radiation dosage.

  • Cause: Software limitation allowed only four radiation blocks, leading to misrepresentations.

  • Outcome: Patch issued treating the issue like a software bug.

3. Patriot Missile System Failure (1991)

  • Date: February 22, 1991

  • Incident: Failure to intercept incoming Iraqi missile

  • Impact: Death of 28 soldiers, injury to 98 others

  • Cause: Software error related to timestamp management affected missile targeting accuracy.

  • Outcome: Error fixed; system re-evaluated to improve reliability.

2. UK Child Support Agency Payment Bugs

  • Date: 1990s

  • Incident: EDS designed a complex payment program leading to severe discrepancies

  • Impact: Overpaid 1.9 million people, underpaid 700,000, with $7 billion in uncollected payments.

  • Cause: Conflicts arose from agency's reconstruction and the advanced program’s incompatibility.