5 Replies Latest reply: Jul 8, 2013 6:57 AM by Linc Davis
Nobby-65 Level 1 (0 points)

Since 06:38 hours yesterday my imac keeps crashing.   The only updates have been from Apple and AVAST but it seems that whenthe mac tries to do a back-up it crashes.   The remote device is avasilable, accessible and ready.  It is accessed vias wi-fi which is strong in signal, stable and I am using the mac when it crashes....


Interval Since Last Panic Report:  11 sec

Panics Since Last Report:          1

Anonymous UUID:                    BC269854-7505-3B58-FAE9-4E378C977C22



Sun Jul  7 08:01:11 2013

panic(cpu 1 caller 0xffffff802f0f0e39): "hfs_getnewvnode: bad ca_blocks (too small)"@/SourceCache/xnu/xnu-2050.24.15/bsd/hfs/hfs_cnode.c:1214

Backtrace (CPU 1), Frame : Return Address

0xffffff80af28b140 : 0xffffff802ee1d626

0xffffff80af28b1b0 : 0xffffff802f0f0e39

0xffffff80af28b2b0 : 0xffffff802f113abc

0xffffff80af28b410 : 0xffffff802f1132fb

0xffffff80af28b4b0 : 0xffffff802ef104f9

0xffffff80af28b520 : 0xffffff802eed7e65

0xffffff80af28bd80 : 0xffffff802eed9a8c

0xffffff80af28bf50 : 0xffffff802f1e16aa

0xffffff80af28bfb0 : 0xffffff802eece9c3



BSD process name corresponding to current thread: backupd



Mac OS version:




Kernel version:

Darwin Kernel Version 12.4.0: Wed May  1 17:57:12 PDT 2013; root:xnu-2050.24.15~1/RELEASE_X86_64

Kernel UUID: 896CB1E3-AB79-3DF1-B595-549DFFDF3D36

Kernel slide:     0x000000002ec00000

Kernel text base: 0xffffff802ee00000

System model name: iMac12,1 (Mac-942B5BF58194151B)



System uptime in nanoseconds: 921097994576

last loaded kext at 108799140173: com.regularrateandrhythm.driver.RowmoteIREmu          1.0 (addr 0xffffff7fb1159000, size 12288)

last unloaded kext at 168809798085: com.apple.driver.AppleUSBUHCI          5.2.5 (addr 0xffffff7faf751000, size 65536)

loaded kexts:

com.regularrateandrhythm.driver.RowmoteIREmu          1.0

com.avast.PacketForwarder          1.3

com.avast.AvastFileShield          2.0.0

com.apple.filesystems.afpfs          10.0

com.apple.nke.asp_tcp          7.1.0

com.apple.driver.AppleBluetoothMultitouch          75.19

com.apple.driver.AppleHWSensor          1.9.5d0

com.apple.driver.AudioAUUC          1.60

com.apple.iokit.IOBluetoothSerialManager          4.1.4f2

com.apple.driver.AGPM          100.12.87

com.apple.driver.AppleMikeyHIDDriver          122

com.apple.filesystems.autofs          3.0

com.apple.driver.AppleHDA          2.3.7fc4

com.apple.iokit.BroadcomBluetoothHCIControllerUSBTransport          4.1.4f2

com.apple.driver.AppleSMCLMU          2.0.3d0

com.apple.driver.AppleUpstreamUserClient          3.5.10

com.apple.driver.AppleSMCPDRC          1.0.0

com.apple.iokit.IOUserEthernet          1.0.0d1

com.apple.kext.AMDFramebuffer          8.1.2

com.apple.driver.AppleMikeyDriver          2.3.7fc4

com.apple.AMDRadeonAccelerator          1.0.8

com.apple.Dont_Steal_Mac_OS_X          7.0.0

com.apple.driver.ApplePolicyControl          3.4.5

com.apple.driver.AppleBacklight          170.2.5

com.apple.driver.AppleLPC          1.6.0

com.apple.driver.ACPI_SMC_PlatformPlugin          1.0.0

com.apple.driver.AppleIntelHD3000Graphics          8.1.2

com.apple.driver.AppleMCCSControl          1.1.11

com.apple.driver.AppleIntelSNBGraphicsFB          8.1.2

com.apple.iokit.SCSITaskUserClient          3.5.5

com.apple.driver.AppleUSBCardReader          3.1.7

com.apple.driver.AppleIRController          320.15

com.apple.AppleFSCompression.AppleFSCompressionTypeDataless          1.0.0d1

com.apple.AppleFSCompression.AppleFSCompressionTypeZlib          1.0.0d1

com.apple.BootCache          34

com.apple.driver.XsanFilter          404

com.apple.iokit.IOAHCIBlockStorage          2.3.1

com.apple.driver.AppleUSBHub          5.5.5

com.apple.iokit.AppleBCM5701Ethernet          3.6.1b4

com.apple.driver.AppleAHCIPort          2.5.2

com.apple.driver.AirPort.Atheros40          600.72.2

com.apple.driver.AppleFWOHCI          4.9.6

com.apple.driver.AppleUSBEHCI          5.5.0

com.apple.driver.AppleEFINVRAM          1.7

com.apple.driver.AppleHPET          1.8

com.apple.driver.AppleRTC          1.5

com.apple.driver.AppleACPIButtons          1.7

com.apple.driver.AppleSMBIOS          1.9

com.apple.driver.AppleACPIEC          1.7

com.apple.driver.AppleAPIC          1.6

com.apple.driver.AppleIntelCPUPowerManagementClient          196.0.0

com.apple.nke.applicationfirewall          4.0.39

com.apple.security.quarantine          2.1

com.apple.driver.AppleIntelCPUPowerManagement          196.0.0

com.apple.security.SecureRemotePassword          1.0

com.apple.driver.AppleBluetoothHIDKeyboard          170.2

com.apple.driver.AppleHIDKeyboard          170.2

com.apple.driver.IOBluetoothHIDDriver          4.1.4f2

com.apple.driver.AppleMultitouchDriver          235.29

com.apple.iokit.IOSerialFamily          10.0.6

com.apple.kext.triggers          1.0

com.apple.driver.DspFuncLib          2.3.7fc4

com.apple.iokit.IOAudioFamily          1.8.9fc11

com.apple.kext.OSvKernDSPLib          1.6

com.apple.iokit.AppleBluetoothHCIControllerUSBTransport          4.1.4f2

com.apple.iokit.IOFireWireIP          2.2.5

com.apple.driver.AppleHDAController          2.3.7fc4

com.apple.iokit.IOHDAFamily          2.3.7fc4

com.apple.iokit.IOSurface          86.0.4

com.apple.iokit.IOBluetoothFamily          4.1.4f2

com.apple.iokit.IOAcceleratorFamily          74.5.1

com.apple.driver.AppleGraphicsControl          3.4.5

com.apple.driver.AppleBacklightExpert          1.0.4

com.apple.driver.AppleSMC          3.1.4d2

com.apple.driver.IOPlatformPluginLegacy          1.0.0

com.apple.driver.IOPlatformPluginFamily          5.3.0d51

com.apple.kext.AMD6000Controller          8.1.2

com.apple.kext.AMDSupport          8.1.2

com.apple.driver.AppleThunderboltEDMSink          1.1.8

com.apple.driver.AppleThunderboltEDMSource          1.1.8

com.apple.driver.AppleSMBusPCI          1.0.11d0

com.apple.driver.AppleSMBusController          1.0.11d0

com.apple.iokit.IONDRVSupport          2.3.7

com.apple.iokit.IOGraphicsFamily          2.3.7

com.apple.iokit.IOSCSIMultimediaCommandsDevice          3.5.5

com.apple.iokit.IOBDStorageFamily          1.7

com.apple.iokit.IODVDStorageFamily          1.7.1

com.apple.iokit.IOCDStorageFamily          1.7.1

com.apple.iokit.IOAHCISerialATAPI          2.5.1

com.apple.driver.AppleThunderboltDPOutAdapter          1.8.9

com.apple.driver.AppleThunderboltDPInAdapter          1.8.9

com.apple.driver.AppleThunderboltDPAdapterFamily          1.8.9

com.apple.driver.AppleThunderboltPCIDownAdapter          1.2.6

com.apple.iokit.IOSCSIBlockCommandsDevice          3.5.5

com.apple.iokit.IOUSBMassStorageClass          3.5.1

com.apple.iokit.IOSCSIArchitectureModelFamily          3.5.5

com.apple.iokit.IOUSBHIDDriver          5.2.5

com.apple.driver.AppleUSBMergeNub          5.5.5

com.apple.driver.AppleUSBComposite          5.2.5

com.apple.iokit.IOUSBUserClient          5.5.5

com.apple.driver.AppleThunderboltNHI          1.7.8

com.apple.iokit.IOThunderboltFamily          2.4.0

com.apple.iokit.IOEthernetAVBController          1.0.2b1

com.apple.iokit.IOAHCIFamily          2.3.1

com.apple.iokit.IO80211Family          530.4

com.apple.iokit.IONetworkingFamily          3.0

com.apple.iokit.IOFireWireFamily          4.5.5

com.apple.iokit.IOUSBFamily          5.6.0

com.apple.driver.AppleEFIRuntime          1.7

com.apple.iokit.IOHIDFamily          1.8.1

com.apple.iokit.IOSMBusFamily          1.1

com.apple.security.sandbox          220.3

com.apple.kext.AppleMatch          1.0.0d1

com.apple.security.TMSafetyNet          7

com.apple.driver.DiskImages          345

com.apple.iokit.IOStorageFamily          1.8

com.apple.driver.AppleKeyStore          28.21

com.apple.driver.AppleACPIPlatform          1.7

com.apple.iokit.IOPCIFamily          2.7.3

com.apple.iokit.IOACPIFamily          1.4

com.apple.kec.corecrypto          1.0

Model: iMac12,1, BootROM IM121.0047.B1F, 4 processors, Intel Core i5, 2.5 GHz, 4 GB, SMC 1.71f22

Graphics: AMD Radeon HD 6750M, AMD Radeon HD 6750M, PCIe, 512 MB

Memory Module: BANK 0/DIMM0, 2 GB, DDR3, 1333 MHz, 0x80CE, 0x4D34373142353737334448302D4348392020

Memory Module: BANK 1/DIMM0, 2 GB, DDR3, 1333 MHz, 0x80CE, 0x4D34373142353737334448302D4348392020

AirPort: spairport_wireless_card_type_airport_extreme (0x168C, 0x9A), Atheros 9380:

Bluetooth: Version 4.1.4f2 12041, 2 service, 18 devices, 1 incoming serial ports

Network Service: Wi-Fi, AirPort, en1

Serial ATA Device: ST3500418AS, 500.11 GB

Serial ATA Device: HL-DT-STDVDRW  GA32N

USB Device: FaceTime HD Camera (Built-in), apple_vendor_id, 0x850b, 0xfa200000 / 3

USB Device: hub_device, 0x0424  (SMSC), 0x2514, 0xfa100000 / 2

USB Device: BRCM2046 Hub, 0x0a5c  (Broadcom Corp.), 0x4500, 0xfa110000 / 4

USB Device: Bluetooth USB Host Controller, apple_vendor_id, 0x8215, 0xfa111000 / 5

USB Device: hub_device, 0x0424  (SMSC), 0x2514, 0xfd100000 / 2

USB Device: Internal Memory Card Reader, apple_vendor_id, 0x8403, 0xfd110000 / 4

USB Device: IR Receiver, apple_vendor_id, 0x8242, 0xfd120000 / 3


More of a Windows man and new to Macs so the above is a little meaningless to me.....


Any ideas anyone?

MacBook Pro, OS X Mountain Lion (10.8)
  • Nobby-65 Level 1 (0 points)

    I have read alot about AVAST being less than helpful on a MAC so I have removed it to see if this was the issue as this had been updated a couple of days before.....


    WIll let you know..... :-)

  • Nobby-65 Level 1 (0 points)

    Well removed AVAST and did a clean shutdown and reboot but still it keep crashing.... also rolled back Battle Nations as this also had been updated recently....


    Interval Since Last Panic Report:  1750 sec

    Panics Since Last Report:          2

    Anonymous UUID:                    BC269854-7505-3B58-FAE9-4E378C977C22



    Sun Jul  7 08:41:32 2013

    panic(cpu 2 caller 0xffffff800faf0e39): "hfs_getnewvnode: bad ca_blocks (too small)"@/SourceCache/xnu/xnu-2050.24.15/bsd/hfs/hfs_cnode.c:1214

    Backtrace (CPU 2), Frame : Return Address

    0xffffff808f7e3140 : 0xffffff800f81d626

    0xffffff808f7e31b0 : 0xffffff800faf0e39

    0xffffff808f7e32b0 : 0xffffff800fb13abc

    0xffffff808f7e3410 : 0xffffff800fb132fb

    0xffffff808f7e34b0 : 0xffffff800f9104f9

    0xffffff808f7e3520 : 0xffffff800f8d7e65

    0xffffff808f7e3d80 : 0xffffff800f8d9a8c

    0xffffff808f7e3f50 : 0xffffff800fbe16aa

    0xffffff808f7e3fb0 : 0xffffff800f8ce9c3



    BSD process name corresponding to current thread: backupd



    Mac OS version:




    Kernel version:

    Darwin Kernel Version 12.4.0: Wed May  1 17:57:12 PDT 2013; root:xnu-2050.24.15~1/RELEASE_X86_64

    Kernel UUID: 896CB1E3-AB79-3DF1-B595-549DFFDF3D36

    Kernel slide:     0x000000000f600000

    Kernel text base: 0xffffff800f800000

    System model name: iMac12,1 (Mac-942B5BF58194151B)



    System uptime in nanoseconds: 463795754893

    last loaded kext at 84560169367: com.regularrateandrhythm.driver.RowmoteIREmu          1.0 (addr 0xffffff7f91b50000, size 12288)

    last unloaded kext at 204426642412: com.apple.driver.AppleUSBUHCI          5.2.5 (addr 0xffffff7f90151000, size 65536)

    loaded kexts:

    com.regularrateandrhythm.driver.RowmoteIREmu          1.0

    com.apple.filesystems.afpfs          10.0

    com.apple.nke.asp_tcp          7.1.0

    com.apple.driver.AppleBluetoothMultitouch          75.19

    com.apple.driver.AudioAUUC          1.60

    com.apple.driver.AppleHWSensor          1.9.5d0

    com.apple.driver.AGPM          100.12.87

    com.apple.driver.AppleMikeyHIDDriver          122

    com.apple.filesystems.autofs          3.0

    com.apple.driver.AppleHDA          2.3.7fc4

    com.apple.iokit.IOUserEthernet          1.0.0d1

    com.apple.driver.AppleUpstreamUserClient          3.5.10

    com.apple.iokit.IOBluetoothSerialManager          4.1.4f2

    com.apple.Dont_Steal_Mac_OS_X          7.0.0

    com.apple.driver.ApplePolicyControl          3.4.5

    com.apple.driver.AppleSMCPDRC          1.0.0

    com.apple.driver.AppleSMCLMU          2.0.3d0

    com.apple.kext.AMDFramebuffer          8.1.2

    com.apple.iokit.BroadcomBluetoothHCIControllerUSBTransport          4.1.4f2

    com.apple.driver.ACPI_SMC_PlatformPlugin          1.0.0

    com.apple.driver.AppleLPC          1.6.0

    com.apple.AMDRadeonAccelerator          1.0.8

    com.apple.driver.AppleMikeyDriver          2.3.7fc4

    com.apple.driver.AppleIntelHD3000Graphics          8.1.2

    com.apple.driver.AppleIntelSNBGraphicsFB          8.1.2

    com.apple.driver.AppleBacklight          170.2.5

    com.apple.driver.AppleMCCSControl          1.1.11

    com.apple.iokit.SCSITaskUserClient          3.5.5

    com.apple.driver.AppleUSBCardReader          3.1.7

    com.apple.driver.AppleIRController          320.15

    com.apple.driver.XsanFilter          404

    com.apple.iokit.IOAHCIBlockStorage          2.3.1

    com.apple.AppleFSCompression.AppleFSCompressionTypeDataless          1.0.0d1

    com.apple.AppleFSCompression.AppleFSCompressionTypeZlib          1.0.0d1

    com.apple.BootCache          34

    com.apple.driver.AppleUSBHub          5.5.5

    com.apple.driver.AppleFWOHCI          4.9.6

    com.apple.iokit.AppleBCM5701Ethernet          3.6.1b4

    com.apple.driver.AirPort.Atheros40          600.72.2

    com.apple.driver.AppleAHCIPort          2.5.2

    com.apple.driver.AppleUSBEHCI          5.5.0

    com.apple.driver.AppleEFINVRAM          1.7

    com.apple.driver.AppleACPIButtons          1.7

    com.apple.driver.AppleRTC          1.5

    com.apple.driver.AppleHPET          1.8

    com.apple.driver.AppleSMBIOS          1.9

    com.apple.driver.AppleACPIEC          1.7

    com.apple.driver.AppleAPIC          1.6

    com.apple.driver.AppleIntelCPUPowerManagementClient          196.0.0

    com.apple.nke.applicationfirewall          4.0.39

    com.apple.security.quarantine          2.1

    com.apple.driver.AppleIntelCPUPowerManagement          196.0.0

    com.apple.security.SecureRemotePassword          1.0

    com.apple.driver.AppleBluetoothHIDKeyboard          170.2

    com.apple.driver.AppleHIDKeyboard          170.2

    com.apple.driver.IOBluetoothHIDDriver          4.1.4f2

    com.apple.driver.AppleMultitouchDriver          235.29

    com.apple.kext.triggers          1.0

    com.apple.driver.DspFuncLib          2.3.7fc4

    com.apple.iokit.IOAudioFamily          1.8.9fc11

    com.apple.kext.OSvKernDSPLib          1.6

    com.apple.iokit.IOSurface          86.0.4

    com.apple.iokit.IOSerialFamily          10.0.6

    com.apple.iokit.IOBluetoothFamily          4.1.4f2

    com.apple.iokit.IOFireWireIP          2.2.5

    com.apple.iokit.AppleBluetoothHCIControllerUSBTransport          4.1.4f2

    com.apple.driver.AppleHDAController          2.3.7fc4

    com.apple.iokit.IOHDAFamily          2.3.7fc4

    com.apple.driver.AppleSMC          3.1.4d2

    com.apple.driver.IOPlatformPluginLegacy          1.0.0

    com.apple.driver.IOPlatformPluginFamily          5.3.0d51

    com.apple.iokit.IOAcceleratorFamily          74.5.1

    com.apple.driver.AppleSMBusPCI          1.0.11d0

    com.apple.driver.AppleThunderboltEDMSink          1.1.8

    com.apple.driver.AppleThunderboltEDMSource          1.1.8

    com.apple.kext.AMD6000Controller          8.1.2

    com.apple.kext.AMDSupport          8.1.2

    com.apple.driver.AppleGraphicsControl          3.4.5

    com.apple.driver.AppleBacklightExpert          1.0.4

    com.apple.iokit.IONDRVSupport          2.3.7

    com.apple.driver.AppleSMBusController          1.0.11d0

    com.apple.iokit.IOGraphicsFamily          2.3.7

    com.apple.iokit.IOSCSIMultimediaCommandsDevice          3.5.5

    com.apple.iokit.IOBDStorageFamily          1.7

    com.apple.iokit.IODVDStorageFamily          1.7.1

    com.apple.iokit.IOCDStorageFamily          1.7.1

    com.apple.iokit.IOAHCISerialATAPI          2.5.1

    com.apple.driver.AppleThunderboltDPOutAdapter          1.8.9

    com.apple.driver.AppleThunderboltDPInAdapter          1.8.9

    com.apple.driver.AppleThunderboltDPAdapterFamily          1.8.9

    com.apple.driver.AppleThunderboltPCIDownAdapter          1.2.6

    com.apple.iokit.IOSCSIBlockCommandsDevice          3.5.5

    com.apple.iokit.IOUSBMassStorageClass          3.5.1

    com.apple.iokit.IOSCSIArchitectureModelFamily          3.5.5

    com.apple.iokit.IOUSBHIDDriver          5.2.5

    com.apple.driver.AppleUSBMergeNub          5.5.5

    com.apple.driver.AppleUSBComposite          5.2.5

    com.apple.iokit.IOUSBUserClient          5.5.5

    com.apple.driver.AppleThunderboltNHI          1.7.8

    com.apple.iokit.IOThunderboltFamily          2.4.0

    com.apple.iokit.IOFireWireFamily          4.5.5

    com.apple.iokit.IOEthernetAVBController          1.0.2b1

    com.apple.iokit.IO80211Family          530.4

    com.apple.iokit.IONetworkingFamily          3.0

    com.apple.iokit.IOAHCIFamily          2.3.1

    com.apple.iokit.IOUSBFamily          5.6.0

    com.apple.driver.AppleEFIRuntime          1.7

    com.apple.iokit.IOHIDFamily          1.8.1

    com.apple.iokit.IOSMBusFamily          1.1

    com.apple.security.sandbox          220.3

    com.apple.kext.AppleMatch          1.0.0d1

    com.apple.security.TMSafetyNet          7

    com.apple.driver.DiskImages          345

    com.apple.iokit.IOStorageFamily          1.8

    com.apple.driver.AppleKeyStore          28.21

    com.apple.driver.AppleACPIPlatform          1.7

    com.apple.iokit.IOPCIFamily          2.7.3

    com.apple.iokit.IOACPIFamily          1.4

    com.apple.kec.corecrypto          1.0

    Model: iMac12,1, BootROM IM121.0047.B1F, 4 processors, Intel Core i5, 2.5 GHz, 4 GB, SMC 1.71f22

    Graphics: AMD Radeon HD 6750M, AMD Radeon HD 6750M, PCIe, 512 MB

    Memory Module: BANK 0/DIMM0, 2 GB, DDR3, 1333 MHz, 0x80CE, 0x4D34373142353737334448302D4348392020

    Memory Module: BANK 1/DIMM0, 2 GB, DDR3, 1333 MHz, 0x80CE, 0x4D34373142353737334448302D4348392020

    AirPort: spairport_wireless_card_type_airport_extreme (0x168C, 0x9A), Atheros 9380:

    Bluetooth: Version 4.1.4f2 12041, 2 service, 18 devices, 1 incoming serial ports

    Network Service: Wi-Fi, AirPort, en1

    Serial ATA Device: ST3500418AS, 500.11 GB

    Serial ATA Device: HL-DT-STDVDRW  GA32N

    USB Device: FaceTime HD Camera (Built-in), apple_vendor_id, 0x850b, 0xfa200000 / 3

    USB Device: hub_device, 0x0424  (SMSC), 0x2514, 0xfa100000 / 2

    USB Device: BRCM2046 Hub, 0x0a5c  (Broadcom Corp.), 0x4500, 0xfa110000 / 4

    USB Device: Bluetooth USB Host Controller, apple_vendor_id, 0x8215, 0xfa111000 / 5

    USB Device: hub_device, 0x0424  (SMSC), 0x2514, 0xfd100000 / 2

    USB Device: IR Receiver, apple_vendor_id, 0x8242, 0xfd120000 / 4

    USB Device: Internal Memory Card Reader, apple_vendor_id, 0x8403, 0xfd110000 / 3


    Back to the drawing board...... :-(

  • Linc Davis Level 10 (184,820 points)

    Your backup volume is corrupt. What is the backup device?

  • Nobby-65 Level 1 (0 points)

    Linc you hit the nail on the head.....


    I use Time Machine and the back-up device which has two partitions kept blocking the connection.   I re-selected the disk in Time Machine and all is well.


    This started to happen after I updated AVAST - not sur eif it was a coincidence but AVAST is now gone and I am on the look-out for a replacement AV scanner.  Any advice?


    Appreicate the reply - thank you.

  • Linc Davis Level 10 (184,820 points)

    1. This comment applies to malicious software ("malware") that's installed unwittingly by the victim of a network attack. It does not apply to software, such as keystroke loggers, that may be installed deliberately by an intruder who has hands-on access to the victim's computer. That threat is in a different category, and there's no easy way to defend against it. If you have reason to suspect that you're the target of such an attack, you need expert help.
    If you find this comment too long or too technical, read only sections 5, 6, and 10.
    OS X now implements three layers of built-in protection specifically against malware, not counting runtime protections such as execute disable, sandboxing, system library randomization, and address space layout randomization that may also guard against other kinds of exploits.

    2. All versions of OS X since 10.6.7 have been able to detect known Mac malware in downloaded files, and to block insecure web plugins. This feature is transparent to the user, but internally Apple calls it "XProtect." The malware recognition database is automatically checked for updates once a day; however, you shouldn't rely on it, because the attackers are always at least a day ahead of the defenders.
    The following caveats apply to XProtect:
    • It can be bypassed by some third-party networking software, such as BitTorrent clients and Java applets.
    • It only applies to software downloaded from the network. Software installed from a CD or other media is not checked.
    3. Starting with OS X 10.7.5, there has been a second layer of built-in malware protection, designated "Gatekeeper" by Apple. By default, applications and Installer packages downloaded from the network will only run if they're digitally signed by a developer with a certificate issued by Apple. Software certified in this way hasn't necessarily been tested by Apple, but you can be reasonably sure that it hasn't been modified by anyone other than the developer. His identity is known to Apple, so he could be held legally responsible if he distributed malware. That may not mean much if the developer lives in a country with a weak legal system (see below.)
    Gatekeeper doesn't depend on a database of known malware. It has, however, the same limitations as XProtect, and in addition the following:
    • It can easily be disabled or overridden by the user.
    • A malware attacker could get control of a code-signing certificate under false pretenses, or could simply ignore the consequences of distributing codesigned malware.
    • An App Store developer could find a way to bypass Apple's oversight, or the oversight could fail due to human error.
    For the reasons given above, App Store products, and other applications recognized by Gatekeeper as signed, are safer than others, but they can't be considered absolutely safe. "Sandboxed" applications may prompt for access to private data, such as your contacts, or for access to the network. Think before granting that access. OS X security is based on user input. Never click through any request for authorization without thinking.
    4. Starting with OS X 10.8.3, a third layer of protection has been added: a "Malware Removal Tool" (MRT). MRT runs automatically in the background when you update the OS. It checks for, and removes, malware that may have evaded the other protections via a Java exploit (see below.) MRT also runs when you install or update the Apple-supplied Java runtime (but not the Oracle runtime.) Like XProtect, MRT is presumably effective against known attacks, but maybe not against unknown attacks. It notifies you if it finds malware, but otherwise there's no user interface to MRT.
    5. XProtect, Gatekeeper, and MRT reduce the risk of malware attack, but they're not absolute protection. The first and best line of defense is always your own intelligence. With the possible exception of Java exploits, all known malware circulating on the Internet that affects a fully-updated installation of OS X 10.6 or later takes the form of so-called "trojan horses," which can only have an effect if the victim is duped into running them. The threat therefore amounts to a battle of wits between you and the malware attacker. If you're smarter than he thinks you are, you'll win.
    That means, in practice, that you never use software that comes from an untrustworthy source, or that does something inherently untrustworthy. How do you know what is trustworthy?
    • Any website that prompts you to install a “codec,” “plug-in,” "player," "extractor," or “certificate” that comes from that same site, or an unknown one, is untrustworthy.
    • A web operator who tells you that you have a “virus,” or that anything else is wrong with your computer, or that you have won a prize in a contest you never entered, is trying to commit a crime with you as the victim. (Some reputable websites did legitimately warn visitors who were infected with the "DNSChanger" malware. That exception to this rule no longer applies.)
    • Pirated copies or "cracks" of commercial software, no matter where they come from, are unsafe.
    • Software of any kind downloaded from a BitTorrent or from a Usenet binary newsgroup is unsafe.
    • Software that purports to help you do something that's illegal or that infringes copyright, such as saving streamed audio or video for reuse without permission, is unsafe. All YouTube "downloaders" are in this category, though not all are necessarily harmful.
    • Software with a corporate brand, such as Adobe Flash Player, must be downloaded directly from the developer’s website. If it comes from any other source, it's unsafe.
    • Even signed applications, no matter what the source, should not be trusted if they do something unexpected, such as asking for permission to access your contacts, your location, or the Internet for no obvious reason.
    6. Java on the Web (not to be confused with JavaScript, to which it's not related, despite the similarity of the names) is a weak point in the security of any system. Java is, among other things, a platform for running complex applications in a web page, on the client. That was always a bad idea, and Java's developers have proven themselves incapable of implementing it without also creating a portal for malware to enter. Past Java exploits are the closest thing there has ever been to a Windows-style virus affecting OS X. Merely loading a page with malicious Java content could be harmful.
    Fortunately, client-side Java on the Web is obsolete and mostly extinct. Only a few outmoded sites still use it. Try to hasten the process of extinction by avoiding those sites, if you have a choice. Forget about playing games or other non-essential uses of Java.
    Java is not included in OS X 10.7 and later. Discrete Java installers are distributed by Apple and by Oracle (the developer of Java.) Don't use either one unless you need it. Most people don't. If Java is installed, disable itnot JavaScript — in your browsers.
    Regardless of version, experience has shown that Java on the Web can't be trusted. If you must use a Java applet for a task on a specific site, enable Java only for that site in Safari. Never enable Java for a public website that carries third-party advertising. Use it only on well-known, login-protected, secure websites without ads. In Safari 6 or later, you'll see a lock icon in the address bar with the abbreviation "https" when visiting a secure site.

    Follow the above guidelines, and you’ll be as safe from malware as you can practically be. The rest of this comment concerns what you should not do to protect yourself from malware.

    7. Never install any commercial "anti-virus" or "Internet security" products for the Mac, as they all do more harm than good, if they do any good at all. Any database of known threats is always going to be out of date. Most of the danger is from unknown threats. If you need to be able to detect Windows malware in your files, use the free software  ClamXav— nothing else.
    Why shouldn't you use commercial "anti-virus" products?
    • Their design is predicated on the nonexistent threat that malware may be injected at any time, anywhere in the file system. Malware is downloaded from the network; it doesn't materialize from nowhere.
    • In order to meet that nonexistent threat, the software modifies or duplicates low-level functions of the operating system, which is a waste of resources and a common cause of instability, bugs, and poor performance.
    • By modifying the operating system, the software itself may create weaknesses that could be exploited by malware attackers.
    8. ClamXav doesn't have these drawbacks. That doesn't mean it's entirely safe. It may report email messages that have "phishing" links in the body, or Windows malware in attachments, as infected files, and offer to delete or move them. Doing so will corrupt the Mail database. The messages should be deleted from within the Mail application.
    ClamXav is not needed, and should not be relied upon, for protection against OS X malware. It's useful only for detecting Windows malware. Windows malware can't harm you directly (unless, of course, you use Windows.) Just don't pass it on to anyone else.
    A Windows malware attachment in email is usually easy to recognize. The file name will often be targeted at people who aren't very bright; for example:
    ClamXav may be able to tell you which particular virus or trojan it is, but do you care? In practice, there's seldom a reason to use ClamXav unless a network administrator requires you to run an anti-virus application.
    9. It seems to be a common belief that the built-in Application Firewall acts as a barrier to infection, or prevents malware from functioning. It does neither. It blocks inbound connections to certain network services you're running, such as file sharing. It's disabled by default and you should leave it that way if you're behind a router on a private home or office network. Activate it only when you're on an untrusted network, for instance a public Wi-Fi hotspot, where you don't want to provide services. Disable any services you don't use in the Sharing preference pane. All are disabled by default.
    10. As a Mac user you don't have to live in fear that your computer is going to be infected every time you install an application, read email, or visit a web page. But neither should you have the false idea that you will always be safe, no matter what you do. The greatest harm done by security software is precisely its selling point: it makes people feel safe. They may then feel safe enough to take risks from which the software doesn't protect them. Nothing can lessen the need for safe computing practices.